TH03 gameplay! 📝 It's been over two years. People have been investing some decent money with the intention of eventually getting netplay, so let's cover some more foundations around player movement… and quickly notice that there's almost no overlap between gameplay RE and netplay preparations? That makes for a fitting opportunity to think about what TH03 netplay would look like:
You'd want UDP rather than TCP for both its low latency and its NAT hole-punching ability
However, raw UDP does not guarantee that the packets arrive in order, or that they even arrive at all
WebRTC implements these reliability guarantees on top of UDP in a modern package, providing the best of both worlds
I'm not too deep into networking to argue here, and it clearly works for Ju.N.Owen. If we do explore other options, it would mainly be because I can't easily get something as modern as WebRTC to natively run on Windows 9x or DOS, if we decide to go for that route.
Matchmaking: I like Ju.N.Owen's initial way of copy-pasting signaling codes into chat clients to establish a peer-to-peer connection without a dedicated matchmaking server. progre eventually implemented rooms on the AWS cloud, but signaling codes are still used for spectating and the Pure P2P mode. We'll probably copy the same evolution, with a slight preference for Pure P2P – if only because you would have to check a GDPR consent box before I can put the combination of your room name and IP address into a database. Server costs shouldn't be an issue at the scale I expect this to have.
Rollback: In emulators, rollback netcode can be and has been implemented by keeping savestates of the last few frames together with the local player's inputs and then replaying the emulation with updated inputs of the remote player if a prediction turned out to be incorrect. This technique is a great fit for TH03 for two reasons:
All game state is contained within a relatively small bit of memory. The only heap allocations done in MAIN.EXE are the 📝 .MRS images for gauge attack portraits and bomb backgrounds, and the enemy scripts and formations, both of which remain constant throughout a round. All other state is statically allocated, which can reduce per-frame snapshots from the naive 640 KiB of conventional DOS memory to just the 37 KiB of MAIN.EXE's data segment. And that's the upper bound – this number is only going to go down as we move towards 100% PI, figure out how TH03 uses all its static data, and get to consolidate all mutated data into an even smaller block of memory.
For input prediction, we could even let the game's existing AI play the remote player until the actual inputs come in, guaranteeing perfect play until the remote inputs prove otherwise. Then again… probably only while the remote player is not moving, because the chance for a human to replicate the AI's infamous erratic dodging is fairly low.
The only issue with rollback in specifically a PC-98 emulator is its implications for performance. Rendering is way more computationally expensive on PC-98 than it is on consoles with hardware sprites, involving lots of memory writes to the disjointed 4 bitplane segments that make up the 128 KB framebuffer, and equally as many reads and bitshift operations on sprite data. TH03 lessens the impact somewhat thanks to most of its rendering being EGC-accelerated and thus running inside the emulator as optimized native code, but we'd still be emulating all the x86 code surrounding the EGC accesses – from the emulator's point of view, it looks no different than game logic. Let's take my aging i5 system for example:
With the Screen → No wait option, Neko Project 21/W can emulate TH03 gameplay at 260 FPS, or 4.6× its regular speed.
This leaves room for each frame to contain 3.6 frames of rollback in addition to the frame that's supposed to be displayed,
which results in a maximum safe ping time of ≈63 ms. According to this site, that's enough for a smooth connection from Germany to any other place in Europe. At this ping, my system could still run the game without slowdown even if every single frame required a rollback, which is highly unlikely.
Any higher ping, however, could occasionally lead to a rollback queue that's too large for my system to process within a single frame at the intended 56.4 FPS rate. As a result, playing anyone in the US is highly likely to involve at least occasional slowdowns. Delaying inputs on purpose is the usual workaround, but isn't Touhou that kind of game series where people use vpatch to get rid of even the default input delay in the Windows games?
So we'd ideally want to put TH03 into an update-only mode that skips all rendering calls during re-simulation of rolled-back frames. Ironically, this means that netplay-focused RE would actually focus on the game's rendering code and ensure that it doesn't mutate any statically allocated data, allowing it to be freely skipped without affecting the game. Imagine palette-based flashing animations that are implemented by gradually mutating statically allocated values – these would cause wrong colors for the rest of the game if the animation doesn't run on every frame.
Implementing all of this into TH03 can be done in one, a few, or all of the following five ways, depending on what the backers prefer. Sorted from the most generic to the most specialized solution (and, coincidentally, from least to most total effort required):
Generic PC-98 netcode for one or more emulators
This is the most basic and puristic variant that implements generic netplay for PC-98 games in general by effectively providing remote control of the emulated keyboard and joypad. The emulator will be unaware of the game, and the game will be unaware of being netplayed, which makes this solution particularly interesting for the non-Touhou PC-98 scene, or competitive players who absolutely insist on using ZUN's original binaries and won't trust any of my modded game builds.
Applied to TH03, this means that players would select the regular hot-seat 1P vs 2P mode and then initiate a match through a new menu in the emulator UI. The same UI must then provide an option to manually remap incoming key and button presses to the 2P controls (newly introducing remapping to the emulator if necessary), as well as blocking any non-2P keys. The host then sends an initial savestate to the guest to ensure an identical starting state, and starts synchronizing and rolling back inputs at VSync boundaries.
This generic nature means that we don't get to include any of the TH03-specific rollback optimizations mentioned above, leading to the highest CPU and memory requirements out of all the variants. It sure is the easiest to implement though, as we get to freely use modern C++ WebRTC libraries that are designed to work with the network stack of the underlying OS.
I can try to build this netcode as a generic library that can work with any PC-98 emulator, but it would ultimately be up to the respective upstream developers to integrate it into official releases. Therefore, expect this variant to require separate funding and custom builds for each individual emulator codebase that we'd like to support.
Emulator-level netcode with optional game integration
Takes the generic netcode developed in 1) and adds the possibility for the game to control it via a special interrupt API. This enables several improvements:
Online matches could be initiated through new options in TH03's main menu rather than the emulator's UI.
The game could communicate the memory region that should be backed up every frame, cutting down memory usage as described above.
The exchanged input data could use the game's internal format instead of keyboard or joypad inputs. This removes the need for key remapping at the emulator level and naturally prevents the inherent issue of remote control where players could mess with each other's controls.
The game could be aware of the rollbacks, allowing it to jump over its rendering code while processing the queue of remote inputs and thus gain some performance as explained above.
The game could add synchronization points that block gameplay until both players have reached them, preventing the rollback queue from growing infinitely. This solves the issue of 1) not having any inherent way of working around desyncs and the resulting growth of the rollback queue. As an example, if one of the two emulators in 1) took, say, 2 seconds longer to load the game due to a random CPU spike caused by some bloatware on their system, the two players would be out of sync by 2 seconds for the rest of the session, forcing the faster system to render 113 frames every time an input prediction turned out to be incorrect.
Good places for synchronization points include the beginning of each round, the WARNING!! You are forced to evade / Your life is in peril popups that pause the game for a few frames anyway, and whenever the game is paused via the ESC key.
During such pauses, the game could then also block the resuming ESC key of the player who didn't pause the game.
Native PC-98 Windows 9x netcode
Equivalent in features to 2), but pulls the netcode from the emulator down into the PC-98 system itself. Just like Ju.N.Owen or Adonis, it would run as a separate 32-bit or 16-bit Windows application that somehow communicates with the game running in a DOS window. This removes the need for emulator-specific integration code and provides real-hardware support for that handful of real-hardware owners who have actually equipped their PC-98 with a network card such as the LGY-98.
This specific card is also low-level-emulated by the 21/W fork of Neko Project, which would allow this type of netplay to be used with official builds of that specific emulator. DOSBox-X currently emulates the apparently hardware-compatible NE2000 card, but disables its emulation in PC-98 mode, most likely because its I/O ports clash with the typical peripherals of a PC-98 system.
As this is just low-level emulation of a network device though, setting up this kind of networking in Neko Project 21/W requires you to install and configure both a TAP driver on the host system, and the whole Windows 9x network stack on the emulated PC-98. Thankfully, the setup is well-documented, and I did manage to get a working Internet connection inside an emulated Windows 95, but it's definitely not foolproof. A more specific guide or setup program would greatly help here.
And that's not the end of the drawbacks:
Netplay would depend on the PC-98 versions of Windows 9x, requiring players to acquire and install another OS on the emulated system.
Porting libdatachannel (and especially the required transport encryption) to Windows 95 will probably involve a bit of effort as well.
As would actually finding a way to access V86 mode memory from a 32-bit or 16-bit Windows process.
Correctly setting up TH03 to run within Windows 95 to begin with can be rather tricky. The GDC clock speed check needs to be either patched out or overridden using mode-setting tools, Windows needs to be blocked from accessing the FM chip, and even then, MAIN.EXE might still immediately crash during the first frame and leave all of VRAM corrupted:
This is probably a bug in the latest ver0.86 rev92β3 version of Neko Project 21/W; I got it to work fine on real hardware. 📝 StormySpace did run on the same emulated Windows 95 system without any issues, though. Regardless, it's still worth mentioning as a symbol of everything that can go wrong.
A matchmaking server would be much more of a requirement than in any of the emulator variants. Players are unlikely to run their favorite chat client on the same PC-98 system, and the signaling codes are way too unwieldy to type them in manually. (Then again, IRC is always an option, and the people who would fund this variant are probably the exact same people who are already running IRC clients on their PC-98.)
Native PC-98 DOS netcode
Conceptually the same as 3), but going yet another level deeper, replacing the Windows 9x network stack with a DOS-based one. This might look even more intimidating and error-prone, but after I got pingand even Telnet working, I was pleasantly surprised at it's much simpler it is when compared to the Windows variant. The whole stack consists of just one LGY-98 hardware information tool, a LGY-98 packet driver TSR, and a TSR that implements TCP/IP/UDP/DNS/ICMP and is configured with a plaintext file. I don't have any deep experience with these protocols, so I was quite surprised that you can implement all of them in a single 40 KiB binary. Installed as TSRs, the entire stack takes up an acceptable 82 KiB of conventional memory, leaving more than enough space for the game itself. And since both of the TSRs are open-source, we can even legally bundle them with the future modified game binaries.
However, all the emulation and matchmaking issues from the Windows 9x approach remain, along with the following issues:
Porting libdatachannel and the required transport encryption to the TEEN stack seems even more time-consuming than a Windows 95 port.
The TEEN stack has no UI for specifying the system's or gateway's IP addresses outside of its plaintext configuration file. This provides a nice opportunity for adding a new Internet settings menu with great error feedback to the game itself. Great for UX, but it's another thing I'd have to write.
Due to the memory requirements of rollback, the netcode should better run as a TSR in Protected Mode, adding yet another technology I'd have to learn about.
The LGY-98 is not the only network card for the PC-98. Others might have more complicated DOS drivers that might not work as seamlessly with the TEEN stack, or have no preserved DOS drivers at all. Heck, the most time-consuming part of the DOS setup was finding the correct download link for the LGY-98 packet driver, as the one link that appears in a lot of places only throws an access denied error these days. If you're interested in funding this variant and are using a non-LGY-98 card on real hardware, make sure you get general Internet working on DOS first.
Porting the game first
As always, this is the premium option. If the entire game already runs as a standalone executable on a modern system, we can just put all the netcode into the same binary and have the most seamless integration possible.
That leaves us with these prerequisites:
1), by definition, needs nothing from ReC98, and I could theoretically start implementing it right now. If you're interested in funding it, just tell me via the usual Twitter or Discord channels.
2), 3), and 4) require at least 100% RE of TH03's OP.EXE to facilitate the new menu code. Reverse-engineering all rendering-related code in MAIN.EXE would be nice for performance, but we don't strictly need all of it before we start. Re-simulated frames can just skip over the few pieces of rendering code we do know, and we can gradually increase the skipped area of code in future pushes.
100% PI won't be a requirement either, as I expect the MAIN.EXE part of the interfacing netcode layer to be thin enough that it can easily fit within the original game's code layout.
5), obviously, requires all of TH03 to be RE'd, decompiled, cleaned up, and ported to modern systems. Currently, TH03 appears to be the second-easiest game to port behind TH02:
Although TH03 already has more needlessly micro-optimized ASM code than TH02 and there's even more to come, it still appears to have way less than TH04 or TH05.
Its game logic and rendering code seem to be somewhat neatly separated from each other, unlike TH01 which deeply intertwines them.
Its graphics seem free of obvious bugs, unlike – again — the flicker-fest that is TH01.
But still, it's the game with the least amount of RE%. Decompilation might get easier once I've worked myself up to the higher levels of game code, and even more so if we're lucky and all of the 9 characters are coded in a similar way, but I can't promise anything at this point.
Once we've reached any of these prerequisites, I'll set up a separate campaign funding method that runs parallel to the cap. As netplay is one of those big features where incremental progress makes little sense and we can expect wide community support for the idea, I'll go for a more classic crowdfunding model with a fixed goal for the minimum feature set and stretch goals for optional quality-of-life features. Since I've still got two other big projects waiting to be finished, I'd like to at least complete the Shuusou Gyoku Linux port before I start working on TH03 netplay, even if we manage to hit any of the funding goals before that.
For the first time in a long while, the actual content of this push can be listed fairly quickly. I've now RE'd:
conversions from playfield-relative coordinates to screen coordinates and back (a first in PC-98 Touhou; even TH02 uses screen space for every coordinate I've seen so far),
the low-level code that moves the player entity across the screen,
a copy of the per-round frame counter that, for some reason, resets to 0 at the start of the Win/Lose animation, resetting a bunch of animations with it,
a global hitbox with one variable that sometimes stores the center of an entity, and sometimes its top-left corner,
and the 48×48 hit circles from EN2.PI.
It's also the third TH03 gameplay push in a row that features inappropriate ASM code in places that really, really didn't need any. As usual, the code is worse than what Turbo C++ 4.0J would generate for idiomatic C code, and the surrounding code remains full of untapped and quick optimization opportunities anyway. This time, the biggest joke is the sprite offset calculation in the hit circle rendering code:
A multiplication with 6 would have compiled into a single IMUL instruction. This compiles into 4 MOVs, one IMUL (with 2), and two ADDs. This surely must have been left in on purpose for us to laugh about it one day?
But while we've all come to expect the usual share of ZUN bloat by now, this is also the first push without either a ZUN bug or a landmine since I started using these terms! 🎉 It does contain a single ZUN quirk though, which can also be found in the hit circles. This animation comes in two types with different caps: 12 animation slots across both playfields for the enemy circles shown in alternating bright/dark yellow colors, whereas the white animation for the player characters has a cap of… 1? P2 takes precedence over P1 because its update code always runs last, which explains what happens when both players get hit within the 16 frames of the animation:
If they both get hit on the exact same frame, the animation for P1 never plays, as P2 takes precedence.
If the other player gets hit within 16 frames of an active white circle animation, the animation is reinitialized for the other player as there's only a single slot to hold it. Is this supposed to telegraph that the other player got hit without them having to look over to the other playfield? After all, they're drawn on top of most other entities, but below the player.
SPRITE16 uses the PC-98's EGC to draw these single-color sprites. If the EGC is already set up, it can be set into a GRCG-equivalent RMW mode using the pattern/read plane register (0x4A2) and foreground color register (0x4A6), together with setting the mode register (0x4A4) to 0x0CAC. Unlike the typical blitting operations that involve its 16-dot pattern register, the EGC even supports 8- or 32-bit writes in this mode, just like the GRCG. 📝 As expected for EGC features beyond the most ordinary ones though, T98-Next simply sets every written pixel to black on a 32-bit write. Comparing the actual performance of such writes to the GRCG would be 📝 yet another interesting question to benchmark.
Next up: I think it's time for ReC98's build system to reach its final form.
For almost 5 years, I've been using an unreleased sane build system on a parallel private branch that was just missing some final polish and bugfixes. Meanwhile, the public repo is still using the project's initial Makefile that, 📝 as typical for Makefiles, is so unreliable that BUILD16B.BAT force-rebuilds everything by default anyway. While my build system has scaled decently over the years, something even better happened in the meantime: MS-DOS Player, a DOS emulator exclusively meant for seamless integration of CLI programs into the Windows console, has been forked and enhanced enough to finally run Turbo C++ 4.0J at an acceptable speed. So let's remove DOSBox from the equation, merge the 32-bit and 16-bit build steps into a single 32-bit one, set all of this up in a user-friendly way, and maybe squeeze even more performance out of MS-DOS Player specifically for this use case.
📝 Over two years since the previous largest delivery, we've now got a new record in every regard: 12 pushes across 5 repos, 215 commits, and a blog post with over 14,000 words and 48 pieces of media. 😱 Who would have thought that the superficially simple task of putting SC-88Pro recordings into Shuusou Gyoku would actually mainly focus on deep research into the underlying MIDI files? I don't typically cover much music-related content because it's a non-issue as far as PC-98 Touhou code is concerned, so it's quite fitting how extensive this one turned out. So here we go, the result of virtually unlimited funding and patience:
So where's the controversy? Romantique Tp obviously made the best and most careful real-hardware SC-88Pro recordings of all of ZUN's old MIDIs, including the original (OST) and arranged (AST) soundtrack of Shuusou Gyoku, right? Surely all I have to do now is to cut them into seamless loops to save a bit of disk space, and then put them into the game? Let's start at the end of the track list with the name registration theme, since it's light on instruments and has an obvious loop point that will be easy to spot in the waveform. But, um… wait a moment, that very first drum note comes a bit late, doesn't it?
At a notated tempo of 96 BPM, these first four beats should take exactly 2.5 seconds, which they do in this seamlessly looping softsynth rendering.
That's… not quite the accuracy and perfection I was expecting. But I think I know what we're seeing and hearing there. Let's look at the first few MIDI events on the drum channel:
Delta Pulse Beat Channel Event
+540 960 2:000 1 Controller { CC 0, value 0 }
+0 960 2:000 1 Controller { CC 32, value 0 }
+0 960 2:000 1 ProgramChange { 37 }
[…]
+0 960 2:000 2 Controller { CC 0, value 0 }
+0 960 2:000 2 Controller { CC 32, value 0 }
+0 960 2:000 2 ProgramChange { 19 }
[…]
+0 960 2:000 3 Controller { CC 0, value 0 }
+0 960 2:000 3 Controller { CC 32, value 0 }
+0 960 2:000 3 ProgramChange { 6 }
[…]
+0 960 2:000 4 Controller { CC 0, value 0 }
+0 960 2:000 4 Controller { CC 32, value 0 }
+0 960 2:000 4 ProgramChange { 2 }
[…]
Also, the fact that GS doesn't put its drums on a non-general voice bank and instead relies on external channel configuration to differentiate drums from pitched instruments is making this Yamaha kid uncontrollably furious. 🤬
Yup. That's the sound of a vintage hardware synth being slow and taking a two-digit number of milliseconds to process a barrage of simultaneous Program Change messages, playing a MIDI file that doesn't take this reality into account and expects program changes to happen instantly.
I can only speak from my own experience of writing MIDIs for hardware synths here, but having the first note displaced by 50 ms is very much not the way a composer would have intended the music to be heard if the note is clearly notated to occur on the beat. If you had told me about such an issue when playing one of my MIDIs on a certain synth, I would have thanked you for the bug report! And I would have promptly released a fixed version of the MIDI with the Program Change events moved back by a beat or two. In the case of Shuusou Gyoku's MIDIs, this wouldn't even have added any additional delay in-game, as all of these files already start with at least one beat of leading silence to make room for setting Roland-specific synth parameters.
OK, but that's just a single isolated bass drum hit. If we wanted to, we could even fix this issue ourselves by splicing the same note from around the loop end point. Maybe this is just an isolated case and the rest of Romantique Tp's recordings are fine? Well…
By the way, this seamless audio player is what consumed most of the two website pushes this time. The rest went to the slightly redesigned main page, whose progress bars now use the cap bar style and the GitHub badge colors.
This one is even worse. Here, the delay is so long relative to the tempo of the piece that the intended five drum hits pretty much turn into four.
This type of issue doesn't even have to be isolated to the very beginning of a piece. A few of the tracks in both the OST and AST start with an anacrusis on just one or two channels and leave the Program Change event barrage at the beginning of the first full measure. In 幻想科学 ～ Doll's Phantom for example, this creates a flam-like glitch where the bass on channel 2 is pretty much on time, but the crash hit on channel 10 only follows 50 ms later, after the SC-88Pro took its sweet time to process all the Program Change events on the channels between:
This is from the arranged soundtrack for a change. In that one, ZUN at least fixed the issue in the final three MIDIs (シルクロードアリス, 魔女達の舞踏会, and 二色蓮花蝶 ～ Ancients) that closed out this rearranging project in May 2001, which spread out their per-channel setup events over at least a single measure before playing any note.
Sure, all of this is barely noticeable in casual listening, but very noticeable if you're the one who now has to cut these recordings into seamless loops. And these are just the most obvious timing issues that can be easily pinpointed and documented – the actual worst aspects are all the minor tempo and timing fluctuations throughout most of the pieces. With recordings that deviate ever so slightly from the tempo defined in the MIDI files, you can no longer rely on mathematically exact sample positions when cutting loops. Even if those positions do work out from time to time, there'd pretty much always be a discontinuity in the waveform at both ends of the loop, manifesting as a clearly audible click. In the end, the only way of finding good loop points in existing recordings involves straining your ears and listening very, very closely to avoid any audible glitches. 😩
But if you've taken a look at the second tabs in the clips above, you will have noticed that we don't necessarily have to be stuck with recordings from real hardware. In late 2015, Roland released Sound Canvas VA, a VST plugin that emulates the classic core of Roland's old Sound Canvas lineup, including the SC-88Pro. As long as we run such a software synthesizer through a quality VST host, a purely software-based solution should be way superior for recording looped BGM:
By moving from real-time recording to an offline rendering paradigm, we get perfectly accurate note timing, as it no longer matters how long the synth takes to produce each output sample.
We stay entirely in the digital realm instead of going from digital (SC-88Pro) to analog (RCA cable) to digital (line-in recording) again, removing any chance for noise or distortion to ruin audio quality.
We get to directly render at 44,100 Hz instead of being limited to the 32,000 Hz signal coming out of the SC-88Pro's DAC. This can be easily noticed in the half-speed video above, whose SCVA version retains significantly more sibilant high-frequency content compared to the more muffled sound of Romantique Tp's recording.
Doing that also makes it feasible to preserve loudness differences between the pieces of a soundtrack instead of eradicating them by normalizing the volume of each individual track to the digital maximum.
Finally, it's much more time-efficient. We simply hit foobar2000's Convert button and get all MIDIs rendered within a few seconds each, instead of having to wait the entire length of a piece.
Any drawbacks? For our use case, all of them are found in the abysmal software quality of everything around the synth engine. As it's typical for the VST industry, Sound Canvas VA is excessively DRM'd – it takes multiple seconds to start up, and even then only allows a single process to run at any given time, immediately quitting every process beyond the first one with a misleading Parameter File1 Read Error message box. I totally believe anyone who claims that this makes SCVA more annoying than real hardware when composing new music. Retro gamers also dislike how Roland themselves no longer sells the 32-bit builds they used to offer for the first few versions. These old versions are now exclusively available through resellers, or on the seven seas.
But as far as the SC-88Pro emulation is concerned, there don't seem to be any technical reasons against it. There is a long thread over at VOGONS discussing all sorts of issues, but you have to dig quite deep to find any clear descriptions of bugs in SCVA's synth engine. Everything I found either only applies to the SC-55 emulation and not the SC-88Pro, was fixed by Roland in the meantime, or turned out to be a fixable bug in a MIDI file.
But wait, we've already heard one obvious difference between the real SC-88Pro and Sound Canvas VA. Let's listen to the very first clip again:
Ha! You can clearly hear a panning echo in the real-hardware recording that is missing from the Sound Canvas VA rendering. That's an obvious case of a core system effect not being reproduced correctly. If even that's undeniably broken, who knows which other subtle bugs SCVA suffers from, right? Case closed, Romantique Tp was right all along, SCVA is trash, real hardware reigns supreme
Actually, let's look closer into this one. Panning delay effects like this are typically reverb-related, but General MIDI only specifies a single controller to specify the per-channel reverb level from 0 to 127. Any specific characteristics of the reverb therefore have to be configured using vendor-specific system-exclusive messages, or SysEx for short.
So it's down to one of the four SysEx messages at the beginning of the MIDI file:
Since these byte strings represent Roland-specific instructions, we can't learn anything from a raw MIDI event dump alone here. No problem though, let's just load these files into some old MIDI sequencer that targeted Roland synths, open its MIDI event list, and then they will be automatically decoded into a human-readable representation…
…or at least that's what I expected. In Yamaha land, XGworks has done that for Yamaha's own XG SysEx messages ever since 1997:
No configuration required. You can even edit the textual Value1 representation and XGworks parses it back into the closest supported value!
But for Roland synths, there's… nothing similar? Seriously? 😶 Roland fanboys, how do you even live?! I mean, they are quick to recommend the typical bloated and sluggish big-name DAWs that take up multiple gigabytes of disk space, but none of the ones I tried seemed to have this feature. They can't have possibly been flinging around raw byte strings for the past 33 years?!
But once you look more into today's MIDI community, it becomes clear that this is exactly what they've been doing. Why else would so many people use the word complicated to describe Roland SysEx, or call it an old school/cryptic communication protocol in hexadecimal format? The latter is particularly hilarious because if you removed the word cryptic, this might as well describe all of MIDI, not just SysEx. Everything about this is a tooling issue, and Yamaha showed how easily it could have been solved. Instead, we get Sound Canvas experts, who should know more about the ecosystem than I do, making the incredible mental leap from "my DAW doesn't decode or easily generate SysEx" to "SysEx is antiquated" to "please just lift up these settings to the VST level and into my proprietary DAW's proprietary project format, that would be so much better"…
Thankfully that's not entirely true. After some more digging and configuration, I found a somewhat workable solution involving a comparatively modern sequencer called Domino:
Open the File → Preferences menu and associate your MIDI output device with a module map. This makes sense for SysEx encoding/generation since it can limit the options in the UI to what's actually available on your target hardware, but is also required for selecting the respective SysEx map into Domino's SysEx decoder. There is no technical reason for this because SC-88Pro SysEx messages can be uniquely identified by the three vendor, device, and model ID bytes that every message starts with, but would be too easy and user-friendly. The perception of SysEx being a black art must be upheld at all costs.
I've kept the garbled text of the partial translation to emphasize the sheer amount of jank involved in this entire process.
Load a MIDI file and let Domino "analyze" it:
Strangely enough, this will take quite a while – on my system, this analysis step runs at a speed of roughly 4.25 KB/s of MIDI data. Yes, kilobytes.
Unfortunately, "control change macro restoration" also seems to mean that you don't get to see any raw bytes when selecting the respective MIDI track in the UI, but at least we get what we were looking for:
…for the most part?
Alright, that's something we can work with. The GS Reset message is something that every Roland GS MIDI should start with, but it's immediately followed by a message that Domino failed to decode? The two subsequent reverb parameters make sense, but panning delays typically have more parameters than just a reverb level and time.
That unknown SysEx message shares much of the same bytes with the decoded ones though. So let's do what we maybe should have done all along, return to caveman, and check the SC-88Pro manual:
The relevant section from page 194. We can see how the address and value correspond to bytes 5-7 and 8 in the SysEx messages. Byte 9 is a checksum and byte 10 signals the end of the message.
And that's where we find what this particular issue boils down to. The missing SysEx message is clearly intended to be a Reverb Macro command, whose value can range from 0 to 7 inclusive on the SC-88Pro, but ZUN tries to specify Reverb Macro #14h, or 20 in decimal. The SC-88Pro manual does not specify what happens if a SysEx message wants to write an invalid value to a valid address, which means that we've firmly entered the territory of undefined behavior. Edit (2024-03-10):Romantique Tp confirmed that the real SC-88Pro clamps these Reverb Macro IDs to the supported range of 0-7. Therefore, the appropriate course of action for guaranteeing the same sound on other Roland synths would be to fix the MIDI file and specify Reverb Macro #7 instead. But since this behavior remains technically undefined, we can still argue about ZUN's intention behind specifying the Reverb Macro like this:
Clearly, ZUN did want to specify a valid Reverb Macro, but made a typo when manually entering the SysEx byte string, as he was forced to do thanks to terrible tooling. He clearly liked the resulting sound though, so the track should still be preserved with the panning reverb intact.
Clearly, the typical behavior for MIDI synths is to ignore invalid and unsupported SysEx messages, because validating user input is an important characteristic of quality software. This is what SCVA does, and what we hear in its rendering is the default hall reverb with ZUN's level and time adjustments. Therefore, SCVA is right, and the fact that we get a panning delay on the real SC-88Pro is a bug in real hardware.
Clearly, ZUN did not care enough about the reverb to specify a valid Reverb Macro. Whether we get the default reverb or a panning delay is an irrelevant performance detail, and does intentionally not matter when it comes to the intended sound of this track – especially since these four SysEx messages are the full extent of Roland GS-specific sound design in this piece, and the rest of it only uses standard MIDI features.
In fact, 32 out of the 39 MIDIs across both of Shuusou Gyoku's soundtrack use this invalid Reverb Macro. The only ones that don't are
both versions of Gates' theme (天空アーミー), which use the equally invalid Reverb Macro #11,
both versions of Milia's theme (プリムローズシヴァ), which use Reverb Macro #0 (Room 1),
and, again, the three arranged MIDIs that ZUN released last (シルクロードアリス, 魔女達の舞踏会, and 二色蓮花蝶 ～ Ancients), which feature a more detailed effect setup with custom chorus and EQ settings. In the case of Reimu's theme, these settings are even commented within the MIDI file.
And that's where this quest seemed to end, until Romantique Tp themselves came in and suggested that I take a closer look at the GS Advanced Editor, or GSAE for short.
Make sure to connect a MIDI input device before starting GSAE, or it will silently crash immediately after this splash screen. At least it accepts any controller, so this might just be a bug instead of the typical user-hostile kind of hardware dongle DRM that is pervasive in today's synth industry. 1999 would seem a bit too early for that, thankfully.
I was aware of this tool, but hadn't initially considered it because it's always described as just a SysEx generator/encoder. In fact, the very existence of such a tool made no sense to me at first, and seemed to prove my point that the usability of GS SysEx was wholly inferior to what I was used to in Yamaha land. Like, why not build at least a tiny and stripped-down MIDI sequencer around this functionality that would allow you to insert SC-88Pro-specific messages at any point within a sequence, and not just the beginning? I can see the need for such a tool in today's world of closed-source DAWs where hardware MIDI modules are niche and retro and are only kept alive by a small community of enthusiasts. But why would its developers guarantee that MIDI composers would have to hop between programs even back in 1997? I can only imagine that they saw how every just slightly advanced MIDI sequencer or DAW back then already used its own project format instead of raw Standard MIDI Files, and assumed that composers would therefore be program-hopping anyway?
However, GSAE does support the import of settings from a MIDI file and features a SysEx history window that decodes every newly processed Roland SysEx byte string, which is all I was looking for. So let's throw in that same MIDI and…
That's the result of sending just the single F0 41 10 42 12 40 01 30 14 7B F7 message at the top.
Now that's some wild numbers. An equally invalid Reverb Character, and Reverb Level and Time values that even exceed their defined range of 0-127? Could it be that GSAE emulates the real-hardware response to invalid Reverb Macros here, and gives us the exact reverb setting we can hear in Romantique Tp's recording? This could even be the reason why GSAE is still used and recommended within today's Roland MIDI sequencing scene, and hasn't been supplanted by some more modern open-source tool written by the community.
In any case, these values have to come from somewhere, so let's reverse-engineer GSAE and figure out the logic behind them. Shoutout to IDR for being a great help with its automatic generation of IDC debug symbols for the Delphi standard library, and even including a few names of application-level widget class methods by reading Delphi-specific type information from the binary. This little sub-project made me also come around to appreciating Ghidra, whose decompiler and data type manager helped a lot and allowed me to find the relevant code section within just a few hours.
A~nd it turns out that the values all come from out-of-bounds accesses into arrays on the stack. If we combine 25, 235, and 132 back into a 32-bit value, we get 0x19EB84, which is the virtual address of the relevant function's stack frame base pointer.
But it gets even more hilarious: If you enable debug text output via Option → Other Options → SMF → Insert text events to setup measures and export these imported settings back into a MIDI file, GSAE not only retains these invalid Reverb Macro IDs, but stringifies them via a simple lookup into a hardcoded string pointer array, again without any bounds checks. The effects of this are roughly what you would expect:
Reverb Macro IDs between 8 and 27 simply insert wrong strings from adjacent string pointer arrays
Reverb Macro 28 crashes GSAE
Reverb Macro 64 causes GSAE to vomit 65,512 bytes of garbage into the MIDI file
In the end, we have Domino not decoding the Reverb Macro message, and GSAE, the premier SysEx tool for Roland synths, responding to it in even more undefined and clearly bugged ways than real hardware apparently does. That's two programs confirming that whatever ZUN intended was never supposed to work reliably. And while we still don't know exactly what these reverb parameters are supposed to be, these observations solve the mystery as far as I'm concerned, and solidify my personal opinion on the matter.
So what do we do now, and which version do we go with? Optimally, I'd offer both versions and turn this controversy into a personal choice so that everybody wins… and Ember2528 agreed and generously provided all the funding to make it happen. 💸
If you haven't picked your favorite yet, here are some final arguments:
The Romantique Tp recordings certainly have something going for them with their provenance of coming from real hardware, and the care that Romantique Tp put into manually recording every single track, warts and all. I wholeheartedly agree that preserving the raw sound of playing the MIDI files into the hardware without thinking about bugs or quirks is an important angle to take when it comes to preservation. It's good that these recordings exist – after all, you wouldn't know which musical elements you'd possibly be missing in an emulation if you have nothing to compare it to. Even the muffled sound in the half-speed clip above can be an argument in their favor, as the SC-88Pro's DAC operates at 32 kHz and you wouldn't expect any meaningful frequency content between 16,000 and 22,050 Hz to begin with. Any frequency content in that range that does remain in Romantique Tp's recording is simply 📝 rolled-off imaging noise added during the ADC's resampling process.
All this is why they are a definite improvement over kaorin's 2007 recordings of only the AST, which used to be the previous reference recordings within the community. Those had all of the same timing issues and more, in addition to being so excessively volume-boosted that 0.15% of the samples across the entire soundtrack ended up clipped. That's 6.25 seconds out of 68:39m being lost to pure digital noise.
Most importantly though: ZUN himself said that only the real SC-88Pro will play back these files as he intended them to sound. This quote is likely where the tagline of Romantique Tp's entire recording project came from in the first place:
> 全てのデエタはSC-88ProもしくはSC-8850（ロオランド社）にて最適に聴けるように調整してあります
> それ以外の音源でも、作者の意図した音ではない場合があります。
— ZUN on 東方幻想的音楽, his old MIDI page
However. ZUN is not exactly known for accurately and carefully preserving the legacy of his series, or really doing anything beyond parading his old games as unobtainable showpieces at conventions. With all the issues we've seen, preferring real hardware is ultimately just that: an angle, and a preference. This is why I disagree with the heavy and uncritical advertising that is mainly responsible for elevating the Romantique Tp recordings to their current reference status within the community, especially if at least half of the alleged superiority of real hardware is founded on undefined behavior that can easily be fixed in the MIDI files themselves if people only bothered to look.
Here's where I stand: MIDI files are digital sheet music first and foremost, not an inferior version of tracker modules where the samples are sold separately. As such, the specific synth a MIDI file was written for is merely a secondary property of the composition – and even more so if the MIDI file contains little to nothing in terms of sound design and mostly restricts itself to the basic feature set of General MIDI. In turn, synth quirks and bugs are not a defined part of the composition either, unless they are clearly annotated and documented in the file itself. And most importantly: If the MIDI file specifies a certain timing and a recording fails to reproduce that timing, then that recording is not an accurate representation of the MIDI file.
In that regard, Sound Canvas VA is not only the closest alternative to the real thing, as a few people in the MIDI and retrogaming scene do have to admit, but superior to the real thing. I'll gladly take clarity and perfect timing accuracy in exchange for minor differences in effects, especially if the MIDI file does not explicitly and correctly define said effects to begin with. If I want a panning delay as part of the reverb, I add the respective and correct SysEx message to define one – and if I don't, I do not care about the reverb. You might still get a panning delay on a certain synth, and you might even prefer how it sounds, but it's ultimately a rendering artifact and not a consciously intended part of the composition. In that way, it's similar to the individual flavor a musician adds to a performance of a piece of classical music.
And as far as the differences in frequency response and resonant filters are concerned: In Yamaha land, these are exactly the main distinguishing factors between vintage WF-192XG sound cards (resembling the real SC-88Pro in these characteristics) and the S-YXG50 softsynth (resembling SCVA). Once I found out about that softsynth and how much clearer it sounded in comparison, I sold that old PCI sound card soon after.
In the interest of preservation though, there's still one more unexplored solution that could be the ideal middle ground between the two approaches:
Play the MIDIs through a real-hardware SC-88Pro again
Capture the actually observed system-exclusive settings that fall within the synth's supported and documented ranges
Insert them back into the MIDI file, creating a new bugfixed version
Re-record that bugfixed version through Sound Canvas VA
Edit (2024-03-10): And since Romantique Tp has confirmed what exactly happens on real hardware, I'm going to do exactly that. These bugfixed Sound Canvas VA renderings will be a free bonus of the single next Shuusou Gyoku push, and will add another angle to the preservation of these soundtracks. In the meantime though, the Sound Canvas VA packs will sound like they do in the preview videos above.
Just to be clear: I'm not suggesting that Romantique Tp should have been the one to cut their recordings into loops, or even just the one who defined where the loop points are supposed to be. On the surface, this seems to be a non-issue, and you'd just pick a point wherever each track appears to loop, right? But with 39 MIDIs to cut and all the financial support from Ember2528, it made sense to also solve this problem more thoroughly, and algorithmically detect provably correct loop points for all of these files. Who knows, maybe we even find some surprises that make it all worth it?
This is the algorithm I came up with:
At a basic level, we loop over the list of MIDI events and return the earliest and longest subrange that is immediately followed by an identical copy.
MIDI players, however, need loop point definitions that use MIDI pulse units rather than event list indices. This is especially necessary for multi-track/SMF Type 1 sequences, which would otherwise require one loop start/end index pair per track, and then it still wouldn't work because some of the tracks might not even have an event at the loop start/end point. This requires the detection algorithm and the player to agree on how to map event indices to time points and back, and simply going for the first event of each pulse (i.e., any event with a nonzero delta time) makes the most sense here. In turn, we can skip any potential start or end events that have a delta time of 0, speeding up the algorithm significantly for typical compositions with a high degree of polyphony.
Naively considering just the raw MIDI events works for MIDI playback. But as soon as we want to cut a recording based on the detected loop points, we need to account for the fact that MIDI playback is inherently stateful. Each of the 16 channels at the protocol level features at least the 128 continuous controllers (CCs) with a 7-bit state, the 14-bit pitch bend controller, and the 7-bit instrument program value, in addition to the global tempo of the piece. As a result, two ranges of events might look identical, but can still sound differently if the events before the first range changed one piece of state which is then only touched again near the end of that range. This requires us to track the full MIDI state at both the start and end of a loop, and reject any potential loop that differs in these states:
In this example, a naive event-level scan would detect a loop between beats 3 and 6 as the same events are immediately repeated between beats 6 and 9. However, the piece starts with the first four notes at a channel volume of 50, which is only set to its later value of 100 on beat 5. Therefore, the actual loop ranges from beat 5 to 8. In turn, the piece needed to be at least 11 beats long to include the full second copy of the looped events and prove the loop as such.
This check can be a bit too strict in some cases, though. A channel might start with one of its CCs at a specific value but then change the same CC to a different value at a later point before playing the first note. In such a case, the detected loop would be delayed to the second CC change even though the initial CC value has no impact on the sound. By filtering these redundant CC changes, we get to move the loop start point of a few tracks (original 夢機械 ～ Innocent Power and arranged 魔法少女十字軍) back by a few seconds, to the position you'd expect.
Finally, we reject any overlong loops that themselves fully consist of multiple successive copies of the first N events.
Shuusou Gyoku's original MIDI files hide the original game's lack of MIDI looping by simply duplicating the looping sections enough times so that a typical player won't notice. The algorithm we have so far, however, would return a much longer loop if a MIDI file contains more than three successive copies of a looping section. The original version of ハーセルヴズ in particular repeats its 8 looping bars a total of 15 times before the MIDI ends, and this condition is necessary to detect the actual 8-bar loop instead of a 56-bar one.
Of course, this algorithm isn't perfect and won't work for every MIDI file out there. It doesn't consider things like differently ordered events within the same MIDI pulse, (non-)registered parameter numbers, or the effect that SysEx messages can have on the state of individual channels. The latter would require the general SysEx decoding logic that I would have liked to have for the research above… actually, let's add an issue and add the project to the order form. I'd really like to see a comprehensive open-source cross-vendor SysEx decoder library in my lifetime.
As for the implementation, I was happy to write some Rust again for a change, as it's a great fit for these standalone greenfield command-line tools that don't have to directly interact with the legacy C++ code bases that this project usually deals with. It's even better if the foundational functionality is not just available in a crate, but in four, with the community already having gone through multiple iterations to arrive at a tried and tested winner. Who knows, maybe I even get to rewrite this website in it one day? Just for the sheer meme value of doing so, of course.
I also enjoyed this a lot from a technical point of view:
You might think that Rust's typical safety guarantees don't matter for the problem at hand. But then you accidentally write -= instead of += for a u32 that starts out at 0, and Rust immediately panics instead of silently underflowing to u32::MAX. This must have saved me at least 5 minutes of debugging the resulting logic error.
As it turns out, my loop detection algorithm is embarrassingly parallel. You might initially think about it in a sequential way because we always want the earliest occurrence of the longest repeating section of MIDI events, which means that each new loop candidate further into the track has to be longer than the previous one. But since we always iterate over the entire MIDI, it makes perfect sense to divide and conquer the problem. Let's split the list of possible loop end points into equal chunks, scan them all in parallel for the earliest and longest loop within that chunk, and then pick the earliest and longest loop among those intermediate results as the final one. In Rust, you don't even have to think much about the chunks, as all of that can be easily done by replacing the iteration with Rayon's parallel fold and adding a reduce() with the same condition for the final step. This sped up the algorithm by exactly the number of cores in my system.
This algorithm works well for the long MIDI files of Shuusou Gyoku's OST that all contain multiple duplicates of their loop section, but it quickly reaches its limit with the AST. Following the classic two-loop + fade-out format, that soundtrack was meant to be played back in generic MIDI players, and not to actually be put back into the game in looped form. Since the loop algorithm did, in fact, find inconsistencies even in the OST, two copies of the apparent loop are sometimes not enough to prove cases where the actual loop ends much later than you think it does. In a few cases, it would be enough to simply remove all volume change events from the fade-out to prove the actual loop, but in others, the algorithm would need MIDI event data far past the end of the fade-out.
However, just giving up and not looping any of these tracks would be equally unfortunate. So how about shifting the question, from what's the best loop in this MIDI file to what's the best loop if the MIDI didn't fade out and instead repeated its apparent second loop a third time? As long as the detected loop in such a pre-processed file ends before the repeated range, it's still a valid loop in terms of the unmodified original.
Ideally, we want to do this pre-processing programmatically with the same Rust library instead of manually editing the MIDI. Many sequencers (and especially XGworks) apply significant changes to a MIDI file's internal structure when saving its internal representation back to a MIDI file, which might even mess with our loop algorithm. So it would be very nice to have a more trustworthy tool that applies only the edit we actually want, and perfectly retains the rest of the MIDI.
And that's how this sub-project turned into a small suite of command-line MIDI operations in the classic Unix filter/pipeline style: Each command reads a MIDI file from stdin, transforms it, and outputs text or the resulting MIDI file on stdout. This way, we gain maximum transparency and reproducibility as I can document the unique pre-processing steps for each AST track by simply providing the command lines. And sure, we're re-encoding and re-decoding the full MIDI sequence at every step along such a pipeline, but computers are fast, Rust and the midly library in particular are ⚡ blazingly fast ⚡, and the usability benefits of this pipeline model far outweigh any theoretical performance drops.
Here's the full list of commands that made it into the resulting mly tool:
cut: Extremely basic removal of MIDI events within a certain range.
dump: Dumps all MIDI events into a textual table. All event lists in this blog post are based on this output.
duration: Shows the duration of a MIDI file in pulses, beats, seconds, and PCM samples.
filter-note: Removes all Note On events within a certain range, retaining all other events. This allows us to generate separate intro and loop MIDIs, whose renderings we can then splice back into a single loopable waveform with no discontinuities, which is not guaranteed when rendering a single MIDI file. This provides the last missing piece needed for rendering perfect, sample-accurate loops through Sound Canvas VA.
loop-find: The loop detection algorithm described above.
loop-unfold: Duplicates MIDI events from a given point to the end of the track. A budget solution for the problem of creating synthetic loops – arbitrary copying of arbitrary subranges to arbitrary destinations would have been undeniably nicer, but also much more complex, and I didn't need that full flexibility for the task at hand.
smf0: Flattening multi-track/SMF Type 1 MIDI sequences into single-track/SMF Type 0 ones. Having this conversion as a distinct operation in our toolset allows other operations to exclusively support SMF Type 0 if a Type 1 implementation would either take significant additional effort or just duplicate the Type 0 flattening algorithm. This group of operations includes loop-find, cut, and even the real-time output for duration because tempo events can theoretically occur on any track.
This feature set should strike a good balance between not spending too much of the Shuusou Gyoku budget on tangential problems, but still offering a decent solution for the problem at hand. As a counterexample, the obvious killer feature – deserializing a dump back into a Standard MIDI File – would have gone way past the budget. While there are crates that free you from the need to write manual parsing code for basic data structures, they would instead require a lot of attribute boilerplate – and if the library that provided the structures doesn't already come with these attributes, you now have to duplicate all the structures, and convert back and forth between the original structures and your copies. Not to mention that we'd still have to write code for the high-level structure of the dump output…
If we put it all together, this is what we can do:
The best loop found in the raw MIDI file spans 4 events and 200 milliseconds. Clearly, this is not the loop we're looking for.
Let's cut off all events from the start of the fade-out to the end, do a loop-unfold copy of all events from the position during the apparent second loop that corresponds to where the fade-out started, and try looking for a loop in that modified MIDI.
The resulting loop is 1:31m long, which is exactly what we were hoping to find.
The note space loop represents the earliest possible event range with equivalent per-channel controller and pitch bend state at both ends. This loop is only appropriate for MIDI players, as its bounds can fall into the middle of notes that are played with a different channel state at the start and end of the loop. This is why it doesn't show any sample positions.
The recording space loop ensures that this doesn't happen. It's also always placed on a Note On event with non-zero velocity, which eases the splicing of separate filter-note recordings. This way, it's enough to remove leading silence from the loop part and mix it exactly at the indicated sample position.
The detected loop is also nowhere close to the cut point at beat 466, matching our condition for validity. All events within the loop came from ZUN's original composition, and the cut/loop-unfold combo merely provided the remaining 63% of events necessary to prove this loop as such.
So, where are these loop quirks that justify why some of these audio files are longer than you'd think they should be? Just listing them as text wouldn't really communicate just how minor these are. It would be much nicer to visualize them in a way that highlights the exact inconsistencies within a fixed range of MIDI measures. Screenshots of MIDI sequencer or DAW windows won't capture these aspects all too well because these programs are geared toward fine-grained editing of single tracks, not visualization of details across all channels.
REAPER's piano roll nicely snaps to a certain range, but good luck picking out the individual lines from the single volume lane at the bottom of the screen, or spotting a 7-point difference. Not to mention that CC #11 (Expression) makes up an equal part of a channel's final perceived volume, which is the metric we'd actually want to visualize.
Typical MIDI visualizers, however, are on the complete opposite end of the spectrum. In recent years, MIDI visualization has become synonymous with the typical Synthesia style of YouTube videos with a big keyboard at the bottom, note bars flying in from the top, and optional fancy effects once those notes hit the top of the keyboard. The Black MIDI community has been churning out tons of identically looking MIDI visualizers in recent years that mainly seem to differ in the programming language they're written in, and in how well they can cope with the blackest of black MIDIs.
Thankfully, most of these visualizers are open-source and have small and manageable codebases. The project with the most GitHub stars and the most generic name seemed to be the best starting point for hacking in the missing features, despite using GLSL shaders which I had no prior experience with. It was long overdue that I did something with GLSL though – it added a nice educational aspect to these hacks, and it still was easier than deciphering whatever the fastest and hyper-optimized Rust visualizer is doing.
Still, this visualizer needed a total of 18 small features and bugfixes to be actually usable for demonstrating Shuusou Gyoku's loop quirks. As such, these hacks turned into yet another tangential sub-project that could have easily consumed another two pushes if I cleaned up the code and published the result. But that would have really gone way past the budget for something that people might not even care about. So here's what we're going to do:
I've added this MIDI visualizer as a new goal to the order form. This goal is eligible for microtransactions, so you don't have to fund a full push to see the first changes committed and released.
The upstream project seems to have been abandoned recently, which is the perfect excuse for not even trying to merge in my sweeping changes with a series of pull requests. The code sure needs a lot of cleanup and deduplication, and especially a more build system-friendly way of embedding its shader source code.
Every backer who supports this goal with at least 0.1 pushes or microtransactions will get a Windows binary with my current hacked-in changes as a preview, immediately after the purchase. Shoutout to the MIT license for letting me do this 😛
As usual, once the code is done, the final cleaned-up version will be available for free for everyone, in both source code and binary release form.
Alright then! Here's how to read the visualizations:
The transparency of each note represents its velocity multiplied by the channel volume and expression. To spot volume inconsistencies, you'd compare the opacity of equivalent notes in the two ranges.
The X-axis of these visualizations uses linear/real time, so the width of each measure represents the exact time it takes to be played relative to the other measures in the visualized range. To spot tempo inconsistencies, you'd compare the distance between the bar lines.
Notes that are duplicated on two or more channels may be colored differently in the loop start and end views. These are rendering order inconsistencies and don't communicate anything about the MIDI.
Stage 1 theme (フォルスストロベリー), original and arranged version: The string and harmonica channels are slightly louder on the apparent first loop than on the others.
Apparent loop:
0:01m – 1:31m
Actual loop:
1:04m – 2:34m
Mei and Mai's theme (ディザストラスジェミニ), arranged version: The one and only quirk that's caused by different notes – the first loop has an E♭ on the slap bass channel in measure 32, but the second loop has a G♭ in the corresponding measure 72.
Apparent loop:
0:01m – 1:02m
Actual loop:
0:50m – 1:51m
Stage 3 theme (華の幻想 紅夢の宙), original and arranged version:
The trumpet channel starts out panned to the center of the stereo field (64), before being left-panned by 25% (48) at 1:04m, where it stays for the rest of the track.
Apparent loop:
0:01m – 1:29m
Actual loop:
1:04m – 2:32m
I didn't come up with a good way of visualizing panning in a 2D plane, so you have to trust your ears with this one.
Marie's theme (機械サーカス ～ Reverie), arranged version: Every apparent loop modulates up by a semitone 16 measures before it ends, and remains in that new key at the start of the next loop, so the piece technically doesn't loop at all. The original stays in G♯m throughout.
Stage 5 theme (カナベラルの夢幻少女), original version: The ritardando near the supposed end of the first loop drops from 145 BPM to 118 BPM, but only to 129 BPM in all further loops.
Apparent loop:
0:01m – 1:39m
Actual loop:
1:33m – 3:11m
Yup, that means that the intro part technically makes almost up the entire apparent loop. ZUN replaced the ritardando with instant tempo changes in the arranged version, which moves the loop to its expected place at the start of the track.
The loop start and end points are in the respective next measure past this range.
Stage 6 theme (アンティークテラー), arranged version: The string channel starts out with the maximum expression of 127, but then only goes up to 120 after some fading notes later in the piece, where it stays for the beginning of the second loop.
Apparent loop:
0:01m – 1:53m
Actual loop:
0:13m – 2:05m
Same here.
VIVIT-captured-'s first theme (夢機械 ～ Innocent Power), arranged version: Has a unique ending section that starts in Gm and then modulates through Em and Fm before it fades out on F♯m.
VIVIT-captured-'s second theme (幻想科学 ～ Doll's Phantom), original and arranged version: Another fade-related 127 vs. 120 expression inconsistency, this time on the orange square channel.
Apparent loop:
0:01m – 1:32m
Actual loop:
1:03m – 2:34m
VIVIT-captured-'s third theme (少女神性 ～ Pandora's Box), original and arranged version: Another tempo inconsistency: A slightly differently shaped ritardando before the bell tree hit in the supposed first loop.
Marisa's theme (魔女達の舞踏会), arranged version: Has a unique 8-bar ending section that is first played in Cm and then loops in C♯m while fading out.
Ending theme (ハーセルヴズ), arranged version: Probably the best-known one out of these, and I'm talking of course about the beautiful ending section. I'm making the executive decision to not loop this track in-game, and letting it fade to silence instead.
Before we package up these looped soundtracks, let's take a quick look at how they would be shown off in the Music Room. The Seihou Music Rooms carry over the per-channel keyboards from TH05, add the current per-channel volume, expression, and pan pot values, and top it off with a fake spectrum analyzer. All of these visualizations rely on MIDI data, and the Music Room would feel very dull and boring without them. Just look at Kioh Gyoku, whose Music Room basically turns into a still image in WAVE mode.
Retaining these visualizations even when playing waveform BGM was very important for me, and not just because it would make for a unique high-quality feature that would break new ground. It can also double as proof that the waveform versions are, in fact, in perfect sync with both the MIDIs they are based on, and, by extension, the respective stage scripts.
However, this would require the game to process the MIDIs and update the internal visualization state without simultaneously playing them back through the WinMM / MME / midiOut*() API. And just like graphics and text rendering, Shuusou Gyoku's original code came with zero architectural separation between platform-independent processing logic and platform-specific playback…
So I accidentally rewrote almost the entire MIDI code to achieve said separation. This also provided a great occasion to modernize this code and add some much-needed robustness for potential MIDI mods, while retaining the original code's approach of iterating over raw SMF byte streams. It might all have been very excessive for a delivery that was supposed to be just about waveform BGM support, but on the plus side, MIDI output is now portable to any other system's MIDI API as well.
Surprisingly though, it was Shuusou Gyoku's original MIDI timing that quickly turned out to be rather inaccurate, and not the waveforms. The exact numbers vary depending on the piece, but the game played back every MIDI about 1% slower than notated, adding about 2 or 3 seconds to their total playback time after 5 minutes. Tempo changes in particular were the biggest causes of desynchronizations with the waveforms…
To understand how this can happen to begin with, we have to look closer at how you're supposed to use the midiOut*() API. This API is as low-level as it gets, only covering the transmission of a single MIDI message to the selected output device right now. There is no concept of note timing at this low level, so it's completely up to the program to parse delta times and tempo change events out of the MIDI file and correctly time the calls to this API for each MIDI message. With all the code that runs between the API and the actual renderer of the synth for every single message, the resulting timing can only ever be an approximation of the MIDI file. This doesn't really matter for the timescales and polyphony levels of typical music because, again, computers are fast, but such an API is fundamentally unsuitable for accurately playing back even just a moderately complex million-note Black MIDI.
Shuusou Gyoku handles this required manual timing in the simplest possible way: It runs a MIDI processing function (Mid_Proc() in the code) at an interval of 10 ms, which processes and instantly sends out all MIDI events that have occurred at any point within the last 10 ms, maintaining merely their order. This explains not only why the original game incremented its MIDI TIMER by multiples of 10, but also the infamous missing drums when playing the soundtrack through the Microsoft GS Wavetable Synth:
ZUN reduced all drum notes to the minimum possible length allowed by the 480 PPQN pulse resolution of these MIDI files.
In regular music notation, this corresponds to 1/1920th notes.
While the exact real-time length in purely mathematical terms depends on the tempo of a piece, it only has to be ≥13 BPM for a 1/1920th note to be shorter than 10 ms.
Therefore, the higher the BPM, the higher the chance that both a drum note's Note On and Note Off messages are sent within the same call to Mid_Proc(), with the respective two midiOut*() API calls only being at best a two-digit number of microseconds apart.
So it only makes sense why cheap MIDI synths that don't even respond to reverb or release time messages completely drop any note with such a short length. After all, at a sampling rate of 44,100 Hz, a note would have to be at least 22.7 µs long to be represented by even a single PCM sample.
This also extends to the visualizations above, and was the reason why I chose to render all drum notes as fixed-size diamonds. Otherwise, they would barely be visible.
But while sending MIDI events in such quantized chunks might not be perfect, it can't be the cause behind multi-second playback slowdowns. Instead, this issue has to boil down to the way Shuusou Gyoku times each individual message, and specifically how it converts between MIDI pulse units and real-time (milli)seconds. pbg's original MIDI code chose to do this in an equally confusing and inaccurate way: it kept two counters that tracked the current MIDI pulse before and after the latest tempo change, used the value of the latter counter to decide which events to process, and only added the pulse equivalent of 10 ms to this counter at the end of Mid_Proc() in the then current tempo. The commit message for my rewritten algorithm details the problems with this approach using nice ASCII art in case you're interested, but in short, the main problem lies in how the single final addition can only consider a single tempo change within each call to Mid_Proc(). If a MIDI file contains tempo ramps with less than 10 ms between each different tempo, the original game would only use the last of these tempo values as the basis for converting the entire 10 ms back into MIDI pulses. Not to mention that maybe MIDI pulses aren't the best unit in a game that still 📝 treats the FPU as lava and doesn't use any fixed-point means of increasing the resolution of the 10 ms→pulse division either…
On the contrary, it's much more accurate to immediately convert every encountered MIDI delta time to a real-time quantity and use that unit for event timing, especially if we want to restrict ourselves to integer math. Signed 64-bit integers are enough to fit the product of the slowest possible MIDI tempo ((224 - 1) µs per quarter note) and the highest possible MIDI delta time (228 - 1) at nanosecond precision (103), with one bit to spare. Then, we arrive at a much simpler timing algorithm:
Each simultaneously playing track gets a next event timer, starting out at 0
When looking at the next event, add the converted nanosecond value of its delta time to this timer
Subtract the equivalent of 10 ms from each track's timer at the beginning of the processing function
As long as the timer is ≤0, process and send the next message
The additive nature of this timer not only naturally allows more than one event to happen within a single Mid_Proc() call, but also averages out any minor timing inconsistencies across the length of a track.
assert(length_of_tempo_message == 3);
uint32_t tempo = 0;
for(int i = 0; i < length_of_tempo_message; i++) {
- tempo += ((tempo << 8) + (*track_data++));+ tempo = ((tempo << 8) + (*track_data++));
}
Yup – the original code performed two additions per byte, which incorrectly added the interim value at every byte to the final result, and yielded a tempo that is ≈0.8% / ≈1 BPM slower than notated in the MIDI file, matching the number we were looking for. That's why the |/OR operator is the safer one to use in such a bit-twiddling context…
But now I'm curious. This is such a tiny bug that is bound to remain unnoticed until someone compares the game's MIDI output to another renderer. It must have certainly made it into other games whose MIDI code is based on Shuusou Gyoku's, or that pbg was involved with. And sure enough, not only did this bug survive Kioh Gyoku's OOP refactoring, but it even traveled into Windows Touhou, where it remained in every single game that supported MIDI playback. Now we know for a fact that pbg's Program Support role in the TH06 credits involved sharing ready-made, finished code with ZUN:
The broken tempo deserialization in the respective latest full versions of TH06 through TH10. And yes, that's TH10 – even though TH09's trial version was the last game to ship MIDI versions of its soundtrack, TH10 still contained all of pbg's MIDI code that originated back in Shuusou Gyoku, before TH11 finally removed it.
Amusingly, ZUN's compiler even started optimizing the combination of left-shifting and addition to a multiplication with 257 for TH09, which even sort of highlights this bug if you're used to reading x86 ASM.
That leaves support for MIDI loop points as the only missing feature for syncing MIDI data with a looping waveform track. While it didn't require all too much code, pbg's original zero-copy approach of iterating over raw MIDI data definitely injected a lot of complexity into the required branches. Multi-track/SMF Type 1 files require quite a bit of extra thought to correctly calculate delta times across loop boundaries that reach past the end of the respective track, while still allowing the real-time delta values to be resynchronized at tempo changes within the loop – and yes, 3 of ZUN's 19 arranged MIDI files actually do use more than one track, so this wasn't just about maximizing MIDI compatibility for mods. I stuck to the original approach mostly as a challenge and to prove that it's possible without first parsing the entire MIDI sequence into a friendlier internal representation, but I absolutely do not recommend this to anyone else.
After hardcoding the loop points detected by mly into the binary, we only need to call Mid_Proc() once per frame in the Music Room and pass the frame delta time instead of the 10 ms constant. And then, we get this:
The MIDI TIMER now shows off the arguably more interesting current MIDI pulse value rather than just formatting the PASSED TIME in milliseconds. Ironically, displaying this value in a constantly counting way takes more effort now – the new nanosecond-based timing code doesn't use any measure of total MIDI pulses anymore, and they don't naturally fall out of the algorithm either. Instead, the code remembers the total pulse value of the last event it processed and adds the real-time duration that has passed since, similar to the original timing algorithm.
This naturally causes the timer to jump from the loop end pulse to the loop start pulse, proving that Mid_Proc() is in fact looping the sequence.
Alright, now we know what to package:
We're going to have 8 BGM packs for each permutation of soundtrack (OST / AST), sound source (Romantique Tp / Sound Canvas VA), and codec (FLAC / Vorbis), making up 1.15 GiB of music data in total.
When looking at the package names, you will notice that I don't particularly highlight the FLAC versions as lossless. And for good reason – the Romantique Tp recordings had dithering and noise shaping applied to them, and the Sound Canvas VA versions will necessarily have to be volume-normalized and quantized to 16-bit during the conversion to FLAC. If we wanted a BGM pack with the actual raw Sound Canvas VA output, we'd have to implement WavPack support, which is the only lossless codec that supports 32-bit float – and even that codec could only compress these files down to 14 MiB per minute of music, or 508 MB for the entire original soundtrack. That's 1.4× the size of an equivalent thbgm.dat!
The whole packaging process will be complex enough to warrant a build system. I'd also like to generate an extensive README file for each package, not least to describe the Sound Canvas VA rendering and loop-cutting process in complete detail.
The AST packs need to bundle the MIDI files from ZUN's site for Music Room visualization. We might as well add a 9th MIDI-only AST pack then, as it will naturally fall out of the packaging pipeline anyway. Some people sure love their MIDI synths, after all.
The OST packs can fall back on the original game's MIDI files from MUSIC.DAT for their Music Room visualization, so there's no need to bundle those and infringe copyright. Ironically, the game will still require a MUSIC.DAT even if you use a BGM pack, if only for the one number in that file that says that Shuusou Gyoku's soundtrack consists of 20 tracks in total.
ZUN didn't arrange タイトルドメイド, so we need to copy the OST version recorded with the respective sound source into the AST pack.
Unfortunately, we still haven't reached the end of the complications and weird issues that haunt Shuusou Gyoku's music:
The original game reads the in-game track title directly out of the first Sequence Name event of the playing MIDI file. The waveform equivalent would be the Vorbis comment TITLE tag, which therefore should exactly match the original track's title, down to the exact placement of whitespace. As usual, if I emphasize minor things like this, it's not without reason: 幻想科学 ～ Doll's Phantom inconsistently uses halfwidth spaces at both sides of the ～, and wouldn't fit into the Music Room's limited space otherwise.
However, the AST MIDI files jam a bunch of other metadata into their Sequence Names, roughly following the format
【 $title 】 from 秋霜玉 for sc88Pro comp.ZUN
The track titles should definitely not appear in this format in-game, but how do we get rid of this format without hardcoding either the names or the magic to parse the names out of this format?
The absolute state of GS SysEx tooling rears its ugly head one final time in three of the AST MIDIs, which for some reason are missing the Roland vendor prefix byte in all of their SysEx messages and are therefore undeniably bugged. There even seemed to be another SysEx-related bug which Romantique Tp explained away, but not this one:
The irony of using invalid Reverb Macros within already invalid SysEx messages is not lost on me.
This is something we should fix even before running these files through Sound Canvas VA in order to render these with the reverb settings that ZUN clearly (and, for once, unironically) intended.
For perfect preservation of the original BGM/gameplay synchronicity, it makes sense for the waveform versions to retain the leading 1 or 2 beats of silence that the original MIDI files use for their SysEx setup. While some of the AST tracks use a slightly different tempo compared to their OST counterparts, they would still be largely in sync as ZUN didn't rearrange the layout of their setup area… except for, once again, the three tracks used in the Extra Stage. Marisa's and Reimu's boss themes aren't too bad with their 4 beats of setup, but シルクロードアリス takes the cake with a whopping 12 beats of leading silence. That's 5 seconds from the start of the Extra Stage to the first note you'd hear. 🐌
2) and 4) could theoretically be worked around in Shuusou Gyoku's MIDI code, but there's no way around editing the MIDI files themselves as far as 3) is concerned. Thus, it makes sense to apply all of the workarounds to the AST MIDIs as part of the BGM build process – parsing the titles out of the 【brackets】, inserting the Roland vendor prefix byte where necessary, and compressing the setup bars in the Extra Stage themes to match their OST counterparts. Adding any hidden magic to the MIDI code would only have needlessly increased complexity and/or annoyed some modder in the future who would then have to work around it.
Ideally, these edits would involve taking the mly dump output, performing the necessary replacements at a plaintext level, and rebuilding the result back into a MIDI file, bu~t we're unfortunately missing the latter feature. Luckily, someone else had the same idea 13 years ago and
wrote a tool in C that does exactly what we need. Getting it to compile in 2024 only required fixing a typical C thing… why are students and boomers defending this antique of a language again? 🙄
The single most glaring issue, however, is the drastic difference in volume between the individual tracks in both soundtracks. While Romantique Tp had to normalize each track to the maximum possible volume individually as a consequence of the recording process, the Sound Canvas VA renderings reveal just how inconsistent the volume levels of these MIDI files really are:
The peak amplitudes of every track in both soundtracks, as rendered by Sound Canvas VA at maximum volume. Looking at these, you might think that kaorin's 2007 recordings were purposely trying to preserve the clipping that would come out of an SC-88Pro if you don't manually adjust the volume knob for each song, but those recordings are still much louder than even these numbers.
So how do we interpret this? Is this a bug, because no one in their right mind would want their music to clip on purpose, and that in turn means that everything about these volume levels is arbitrary and unintentional? Or is this a quirk, and ZUN deliberately chose these volume levels for compositional reasons? It certainly would make sense for the name registration theme.
Once again, the AST version of シルクロードアリス is the worst offender in this regard as well, but it might also provide some evidence for the quirk interpretation. The fact that almost all of its MIDI channels blast away at full volume might have been an accident that could have gone unnoticed if the volume knob of ZUN's SC-88Pro was turned rather low during the time he arranged this piece, but the excessive left-panning must have been deliberate. Even Romantique Tp agrees:
It might have even made compositional sense if Silk Road Alice was supposed to be a "Western-style piece", but it's not.
And that's with the volume already normalized. Because this one channel of this one track is almost twice as loud as anything else in the AST, we would consequently have to bring down the volume of every other arranged track and the right channel of the same track by almost 50% if we wanted to maintain the volume differences between the individual tracks of the AST. In the process, we lose almost one entire bit of dynamic range. At this rate, you might even consider remixing and remastering the entire thing, but that would involve so many creative decisions to definitely fall into fanfiction territory…
However, normalizing each track to a peak level of 0 dBFS makes much more sense for in-game playback if you consider how loud Shuusou Gyoku's sound effects are. Once again, the best solution would involve offering both versions, but should we really add two more SCVA BGM packs just to cover volume differences? ReplayGain solves this exact problem for regular music listening in a non-destructive way by writing the per-track and per-album gain levels into an audio file's metadata. Since we need metadata support for titles anyway, we can do something similar, albeit not exactly the same for two reasons:
ReplayGain is specified to target an average volume of −17 dBFS, whereas we'd like to target a peak volume of 0 dBFS in order to always use the entire available digital scale. We've got some loud sound effects to compete with, after all.
ReplayGain expresses its gain values in dB, which is cumbersome to work with. In the realm of PCM, volume changes don't need to involve more than a simple multiplication, so let's go with a simple scalar GAIN FACTOR.
And so, we hard-apply the volume-level gain during the conversion from 32-bit float to FLAC to preserve the volume differences between the tracks, calculate the track-levelGAIN FACTOR based on the resulting peak levels, add a volume normalization toggle to the Sound / Config menu, enable it by default, and thus make everyone happy. ✅
The final interesting tidbit in building these packages can be found in the way the Sound Canvas VA recordings are looped. When manually cutting loops, you always have to consider that the intro might end with unique notes that aren't present at the end of the loop, which will still be fading out at the calculated loop start point. This necessitates shifting the loop start point by a few bars until these notes are no longer audible – or you could simply ignore the issue because ZUN's compositions are so frantic that no one would ever notice.
With the separate intro and loop files generated by mly, on the other hand, the reverb/release trails are immediately visible and, after trimming trailing silence, exactly define the number of samples that the calculated loop start point needs to be shifted by. The .loop file then remains always exactly as long, in samples, as the duration of the loop reported by mly. If a piece happens to have a constant tempo whose beat duration corresponds to an integer number of samples, we get some very satisfying, round loop durations out of this process. ☺️
So let's play it all back in-game… and immediately run into two unexpected miniaudio limitations, what the…?!
miniaudio uses a fixed linear function for its fade-out envelope, and doesn't offer anything else? We might not even want a logarithmic one this time because symmetry with MIDI's simple quadratic curve would be neat, but we sure don't want a linear function – those stay near the original volume for too long, and then turn quiet way too quickly.
There is no way to access FLAC metadata from miniaudio's public API, even though the library bundles the author's own FLAC library which has this feature?
📝 Back when I evaluated miniaudio, I alluded that I consider single-file C libraries to be massively overrated, and this is exactly why: Once they grow as massive as miniaudio (how ironic), they can quickly lead to their authors treating their dependencies as implementation details and melting down the interfaces that would naturally arise. In a regular library, dr_flac would be a separate, proper dependency, and the API would have a way to initialize a stream from an externally loaded drflac object. But since the C community collectively pretends that multi-file libraries are a burden on other developers, miniaudio ended up with dr_flac copy-pasted into its giant single file, with a silly ma_ namespacing prefix added to all its functions. And why? Did we have to move so far in the other direction just because CMake doesn't support globbing? That's a symptom of CMake not actually solving any problem, not a valid architectural decision that libraries should bend around. 🙄
So unless we fork and hack around in miniaudio, there's now no way around depending on a second, regular copy of dr_flac. Which has now led to the same project organization bloat that single-file libraries originally set out to prevent…
Sigh. At this rate, it makes more sense to just copy-paste and adapt the old BGM streaming code I wrote for thcrap in late 2018, which used dr_flac directly, and extend it with metadata support. With the streaming code moved out of the platform layer and into game logic, it also makes much more sense to implement the squared fade-out curve at that same level instead of copy-pasting and adjusting an unhealthy amount of miniaudio's verbose C code.
While I'm doing the same for the old Vorbis streaming code, it would also make sense to rewrite that one to use stb_vorbis instead of the old libogg+libvorbis reference libraries. There's no need to add two more dependencies if miniaudio already comes with stb_vorbis.c, and that library is widelyacclaimed. So, integration should be a breeze, right?
Well, surprise, rarely have I seen a C library so actively hostile toward being integrated. Both of its API variants are completely unreasonable:
The pulldata API pulls Vorbis data as needed from either a memory buffer containing the entire Vorbis file, or a C FILE* handle.
Effectively, this forces either you to give up disk streaming completely, or your program into C's terrible I/O API with all its buffering slowness and Unicode issues on Windows. The documentation even goes on to suggest just modifying the code if you need anything else, which might be acceptable in the strange world of game development this library originates from, but it sure isn't in the kind of open-source development I do.
The pushdata API expects the caller to gradually feed chunks of Vorbis data. How large do these chunks have to be? Nobody knows – and, even worse, the API doesn't retain any of the data already pushed in. If the buffer you passed is too small, which you don't get to know in advance, you have to pass the same data plus more in the next call. I get that you might want an API like this to avoid dynamic memory allocations, but not only does this API perform plenty of allocations itself, it actively forces its caller to realloc() over and over again. 🙄 The lack of seeking support reveals that this API is geared towards live-streamed audio, and it might very well be acceptable in such a case, but it's nothing we could use for BGM.
What happened to the tried-and-true idea of providing a structure with read, tell, and seek callbacks, and then providing an optional variant for C FILE* handles if you absolutely must? Sure, the whole point of Vorbis is to be small and nobody these days would care about spending a few MB on keeping an entire Vorbis file in memory, but come on. If pulldata made the deliberate and opinionated choice to only support buffers of complete Vorbis streams and argued in the name of simplicity that hand-coded disk streaming isn't worth it in this day and age, I might have even been convinced. And this is from the guy who popularized the concept of single-file C libraries in the first place?
Oh well, tupblocks go brrr. libvorbis definitely shows its age with all the old command-line tools in the lib/ directory that they never moved away and that we now have to remove from our glob. But even that just adds a single line to the Tupfile, and then we get to enjoy its much friendlier API. That sure beats the almost 800 lines of code that miniaudio had to write to integrate stb_vorbis… which I can't even link because the file is too big for GitHub. 🤷
At this point, it would have even made sense to upgrade from a 24-year-old lossy codec to an 11-year-old lossy codec and use Opus instead, since the enforced 48,000 Hz sampling rate is a non-issue when you control the entire audio pipeline. But let's keep compatibility with existing thcrap mods for now.
In the end, the Windows build ended up using only a single one of the miniaudio features that DirectSound doesn't have, and that's the ability to use the more modern WASAPI instead of DirectSound. We're still going to use miniaudio for the Linux port, but as far as Windows is concerned, it would be quite nice to backport BGM streaming to the game's original DirectSound backend. The P0275 build is pushing 1 MiB of binary size for a game that originally came in a 220 KiB binary, so it would remove a noticeable amount of bloat from GIAN07.EXE, but it would also allow waveform BGM to work in the Windows 98-compatible i586 build. If that sounds cool to you, this is the issue you want to fund.
That only left some logic and UI busywork to put it all together, which means that we've almost reached the end of things to talk about! Here's what it all looks like:
BGM pack selection is done in-game through a new submenu. The <Download> option will open the BGM pack release page in the system's preferred browser:
This window presented a great occasion for already implementing the generic boilerplate for vertically scrolling windows with an unlimited number of items. That will come in quite handy once we introduce better replay support… 👀
Even with per-track BGM volume normalization, Shuusou Gyoku's sound effects are still a bit too loud in comparison, especially when mixed on top of that excessively and unfixably left-panned AST version of the Extra Stage theme. Adding separate volume controls for BGM and sound effects really was the only sustainable solution here, and conveniently checks an important quality-of-life box the original game lacked. So important that it was the very first issue I added to the GitHub tracker of my fork:
I really wanted to have Japanese help text in these menus, as it makes them look just so much more consistent and polished. Many thanks to Elfin, who responded to my bounty offer, and will most likely also provide localizations for future features.
In-game music titles are now consistently right-aligned. Leading whitespace in 4 of the original MIDI Sequence Names suggests that pbg might have intended these titles to be centered within the 216 maximum pixels that the original code designated for music titles, but none of those 4 had the correct amount of spaces that would have been required for exact centering:
Right-aligned text matches the one certain intention I can read out of the code, and allows us to consistently trim whitespace from both the original MIDI Sequence Names and the TITLE tags in the BGM packs… at the cost of significantly changing the animation. 🤔
Maybe, all this whitespace had the explicit purpose of making the animation look the way it did originally? But hard-padding the title tags in the BGM packs would be so dumb… 😩 Let's keep it like this for now and fix the animation later.
At startup, the game now shows a new screen if any of the game's .DAT files are missing, displaying their expected absolute path. This is bound to be very important on Linux because each distribution might have its own idea of where these files are supposed to be stored. But even on Windows, this allows GIAN07.EXE to at least run and show something if one or more of these files are not present, instead of crashing at the first attempt of loading anything from them.The ¥ instead of \ is, 📝 once again, a font issue. Good luck finding a font not named MS Gothic that looks good when rendered in this game…
On a more unfortunate note, I dropped the i586 build from this release. Visual Studio 2022's CRT implements the new filesystem and threading code using Win32 API functions that are only available on Vista or later and are not covered by the one ready-made KernelEx package I was able to find, so I couldn't easily test such a build on Windows 98 anymore. Resurrecting the i586 build would therefore involve additional platform abstraction layers that we wouldn't need otherwise. Writing them wouldn't be too expensive, but it only makes sense if there's actual demand. Backporting waveform BGM to DirectSound to restore feature parity would also be a good idea here, as it would avoid the need to litter the current code with #ifdefs at any place that references anything related to BGM packs.
After half a year of being bought out way past the cap, I've finally got some small room left for new orders again. If it weren't for this blog post and the required research and web development work, this delivery would have probably come out in early January, taking half the time it ended up taking. So I really have to start factoring the blog posts into the push prices in a better and fairer way.
Meanwhile, the hate toward my day job only keeps growing, but there's little point in looking for a new one as long as ReC98 remains this motivating and complex. It leaves pretty much no cognitive room for any similarly demanding job. Thus, I want 2024 to be the year where ReC98 either becomes profitable enough to be my only full-time job, or where we conclusively find out that it can't, I go look for a better day job, and ReC98 shifts to a slower pace. Here's the plan:
From now on, I will immediately increase the push price whenever we reach 100% of the cap, either directly through new orders or indirectly through existing subscriptions. The price increase will be relative to how long it took to reach that point since the last re-opening.
If the store continues selling out, I will aim for per push by the end of the year.
In exchange, microtransactions (i.e., deliveries containing just code and no blog posts) will now be half the price of regular pushes for the same amount of delivered code. Or in other words: If you want to fund a goal that's eligible for microtransactions, you can now decide whether your fixed amount of money goes to 2× coding work and 0× blogging, or 1× coding work and 1× blogging.
I'll permanently increase the default level of the cap from 8 to 10 pushes. The past 12 months were full of mod releases that raised the bar, and 2024 shows no signs of stopping that trend.
If we ever reach per push, I plan to hire people for some of the contribution-ideas or anything else that might improve this project. (Well-produced YouTube videos about the findings of this project might be a nice idea!) At that point, I will have reached my goal of living decently off this project alone, and it's time for others to make money in this space as well.
With the new price of per push, this means that there's now a small window in which you can get a full push worth of functionality for , until the current cap is filled up again.
Next up: Probably TH02's endings to relax a bit. Maybe we're also getting some new Touhou-related contributions?
📝 Posted:
🏷 Tags:
Yet another small interruption before we get to Shuusou Gyoku, but only
because I've got a big announcement to make! Touhou Patch Center has just
commissioned the basic feature set that would allow PC-98 Touhou to be
translated into non-ASCII languages. 💰 And we're in fact doing it on PC-98,
and don't wait for the games to be ported to other systems first.
How is this going to work?
This project will start sometime after I've completed the current big
project of porting Shuusou
Gyoku to Linux, so probably during the summer of 2024. Similar to
the previous MediaWiki update, this will bypass the ReC98 push and cap
model: Touhou Patch Center is going to guarantee a minimum budget out of
their Open Collective funds, which can be increased with further donations
from the community, and I'm going to send an invoice once I'm done. In
addition, I'm also going to keep in contact with all interested translators
and backers via a Discord room throughout the process for additional
technical quality control. Edit (2024-04-11): Over the last few months, I've focused all unconstrained RE funding on increasing the amount of moddable text-related code. As a result, the translation project could now cover the majority of text in PC-98 Touhou, including:
With still a bit of time left until the Shuusou Gyoku Linux port is done,
I'll put any general and unconstrained reverse-engineering,
position independence, or anything contributions that come in during
the next few months towards covering everything that's still missing there:
TH04's and TH05's MAINE.EXE contains some not
yet RE'd text in their verdict screens. 1.5 pushes there, since it's
unfortunately contained in the same function that also performs the highly
complex skill value calculation.
TH05's Extra Stage ending is followed by an All Cast screen listing the characters of all 5 games, to the tune of Peaceful Romancer. Shouldn't take longer than 0.5 pushes.
TH03's MAINL.EXE needs 100% PI to enable convenient
translations of the win messages, the character titles and names at the
beginning of a stage, the Stage 8/9 cutscenes, and the endings. Let's go
with 2 pushes there just to be safe, and finalize the missing code to not 📝 incur more technical debt.
Technically, we'd need TH02's MAIN.EXE to be 100%
position-independent for any translation-related code modifications, but
reaching that goal before I get to work on translation support is probably
unrealistic. However, this new translation code needs to work across 13
executables to begin with, so I'm going to put most of it into a
separate TSR program anyway. Including this TSR in a non-PI'd executable
shouldn't be that painful, then.
The same is true for TH03's MAIN.EXE, but the ＷＩＮＮＥＲ ＢＯＮＵＳ popup is the only translatable piece of text there. Should be even less of a problem.
TH04's and TH05's High Score menus contain a single string about scores not being recorded in Slow Mode (スローモードでのプレイでは、スコアは記録されません). Regularly, this means that we'd have to decompile the whole menu, together with TH05's intricate "glyph ball" animation, which would be way too excessive just for this one string. If the Shuusou Gyoku Linux port gets done sooner than this gets decompiled, I'll figure something out.
In total, that's the next 4 general pushes that will go towards ensuring
translatability of most of PC-98 Touhou. If you'd like your
contribution (or existing subscription) to go to gameplay code instead, be sure to tell me!
What's the minimum guaranteed set of features?
The main feature will be a custom renderer for a subsetted, monospaced
Unicode bitmap font, and its integration into any translatable part of the
game. For the script files, this means UTF-8 support with Shift-JIS
fallback. For the glyphs, I'll use GNU Unifont by default, but we
could also use any other freely licensed bitmap font with 8×16 or 16×16
glyphs for alphabets of certain languages. Everything about this will be the
real deal: The system will potentially support all of Unicode without font
ROM hacks so that the translations will work on real hardware, and there
will be no shortcuts for just a few Latin characters. And if someone wants
to translate this game into a language with more complex
shaping rules, I'll make sure that they look pretty as well if there's
some budget left.
This will allow translation teams to build static translation patches into
any language by editing the original script files, and using
-Tom-'s existing
tools for any images. Modifications of hardcoded strings would still
require recompiling the binary, and each group would have to distribute and
advertise the result on their own.
🌐
Which languages are we getting?
As of 2023-10-10, the following translators and teams have expressed
interest:
Spanish, Latin American: Xziled, DarkeyeSide, Mr. Tremolo
Measure
Vietnamese: Shinka
Wait, Arabic?! On my PC-98?! What's the plan there?
The two challenges with Arabic scripts are transforming
a text to use the codepoints for contextual glyph forms
(shaping), and right-to-left rendering. Shaping requires not too
much code, which is easily added to the font subsetting build step.
Right-to-left rendering, on the other hand, must be a feature of the new
PC-98-native text renderer, because there are several places in PC-98 Touhou
where text is gradually typed character-by-character. So it will require a
bit of dedicated budget, but not all too much from what I can tell. Bidirectional
textwould add a great deal of complexity here, but we most
likely won't need to implement it – I'll simply pick a direction based
on the
first codepoint on a line, and ask translators to manually reverse
any Latin-script runs of text in the middle of an Arabic-script line.
How much better could it all be?
The most important feature: We could finally move away from the concept
of translation patches, integrate all translations as part of the
ReC98 repo, and ship them directly as part of new ReC98 builds. Languages
could then be switched at runtime, through a new setting in the Option
menu.
And why stop there? How about binding a keyboard key to a new
language selection window that can be opened at any point during the
game, and even switches out any text that is currently shown on
screen?
I could finally translate a
canon Touhou game via a gettext-like dictionary
system. This would allow modded source text to override translations, and
even make it possible to translate mods as well.
Ideally, all translators I get to work with are highly motivated and
finish translating each game they start, so that we don't even have to think
about translation
stacking, but maybe we still should.
We could use proportional fonts instead of aligning every glyph to the
8×16 text RAM grid. Unlike the Windows Touhou games where proportional fonts
are crucial because adding more text space would desync replays, they are
not that important in PC-98 Touhou. With no replays to be desynced,
we can arbitrarily add new boxes without worrying about the font.
However, supporting proportional fonts would make it possible to
lift some of the text sprites into the custom font system, allowing
their glyphs to be shared more easily across languages:
Some of the image text from TH03's, TH04's, and TH05's main menus.
Turning these sprites into text so that translators won't have to
manually shift pixels around may or may not be worth it.
On the topic of new text boxes: Automatic line and box breaks at word
boundaries would completely remove the need for in-game proofreading.
In-game TL notes… nah, probably not. Where would we even put them in the
original screen layout?
Due to the continued interest in TH01's Anniversary Edition, any code
modifications would be exclusive to a respective game's bugfixed
anniversary branch – i.e., any translated builds will be
bundled with a growing number of fixes for issues in the original games that
fall under my
current definition of bugs. This avoids a combinatorial explosion
of the number of branches, merges, and releases I'd have to do. For a small
amount of extra money though, I could merge them back to the ZUN
bug-preserving debloated branch. And for a lot of extra
money, I could reimplement everything on master while
preserving the original memory layout of ZUN's original binaries. This would
allow the translation-supporting binaries to be easily diffed against the
original ones, and retain compatibility with existing hacks or cheat tables.
The latter was already something that
📝 the Shuusou Gyoku community previously expected my recompiled builds to have.
I could top off the project with some smaller, more intricate
localizations that translators might request for certain languages. Most
notably, this category would include any localization of TH01's
東方★靈異伝,
STAGE #, and
HARRY UP popups that goes beyond just
fixing the Engrish.
The previous static English patches from 2014 introduced quite a few
fanfiction changes that have been interpreted as canon in the years since. I
could write a blog post to highlight these, and also compare the translation
as a whole with the more literal English translation we're likely to get
this time around.
Finally, if you all really want to, I could move all translatable
content to the Touhou Patch Center interface, which would truly turn that
site into the one central translation source for all canon Touhou games.
Automatic updates won't be feasible before porting away the games from PC-98
hardware, so the thpatch server would have to communicate with the ReC98
repo via a GitHub webhook. This will be rather expensive though, as I'd also
have to set up some kind of build/release CI for ReC98 first.
These features are mostly independent of each other, and it will be up to
Touhou Patch Center to pick a priority order. That's also where all of you
could come in and influence this order with your donations. So it's closer
to a traditional crowdfunding campaign with stretch goals, where the sky is
the limit, than it is to the usual ReC98 model. And while there can be no
fixed prices for any of the goals, you can be sure that anything you invest
will improve the quality of the final product.
From now on, this will be the only way of funding any translation-related
goals; I've removed the respective options from the ReC98 order form.
Looking forward to how many of these additional ideas I get to implement –
but, as always, please invest responsibly.
Well, well. My original plan was to ship the first step of Shuusou Gyoku
OpenGL support on the next day after this delivery. But unfortunately, the
complications just kept piling up, to a point where the required solutions
definitely blow the current budget for that goal. I'm currently sitting on
over 70 commits that would take at least 5 pushes to deliver as a meaningful
release, and all of that is just rearchitecting work, preparing the
game for a not too Windows-specific OpenGL backend in the first place. I
haven't even written a single line of OpenGL yet… 🥲
This shifts the intended Big Release Month™ to June after all. Now I know
that the next round of Shuusou Gyoku features should better start with the
SC-88Pro recordings, which are much more likely to get done within their
current budget. At least I've already completed the configuration versioning
system required for that goal, which leaves only the actual audio part.
So, TH04 position independence. Thanks to a bit of funding for stage
dialogue RE, non-ASCII translations will soon become viable, which finally
presents a reason to push TH04 to 100% position independence after
📝 TH05 had been there for almost 3 years. I
haven't heard back from Touhou Patch Center about how much they want to be
involved in funding this goal, if at all, but maybe other backers are
interested as well.
And sure, it would be entirely possible to implement non-ASCII translations
in a way that retains the layout of the original binaries and can be easily
compared at a binary level, in case we consider translations to be a
critical piece of infrastructure. This wouldn't even just be an exercise in
needless perfectionism, and we only have to look to Shuusou Gyoku to realize
why: Players expected
that my builds were compatible with existing SpoilerAL SSG files, which
was something I hadn't even considered the need for. I mean, the game is
open-source 📝 and I made it easy to build.
You can just fork the code, implement all the practice features you want in
a much more efficient way, and I'd probably even merge your code into my
builds then?
But I get it – recompiling the game yields just yet another build that can't
be easily compared to the original release. A cheat table is much more
trustworthy in giving players the confidence that they're still practicing
the same original game. And given the current priorities of my backers,
it'll still take a while for me to implement proof by replay validation,
which will ultimately free every part of the community from depending on the
original builds of both Seihou and PC-98 Touhou.
However, such an implementation within the original binary layout would
significantly drive up the budget of non-ASCII translations, and I sure
don't want to constantly maintain this layout during development. So, let's
chase TH04 position independence like it's 2020, and quickly cover a larger
amount of PI-relevant structures and functions at a shallow level. The only
parts I decompiled for now contain calculations whose intent can't be
clearly communicated in ASM. Hitbox visualizations or other more in-depth
research would have to wait until I get to the proper decompilation of these
features.
But even this shallow work left us with a large amount of TH04-exclusive
code that had its worst parts RE'd and could be decompiled fairly quickly.
If you want to see big TH04 finalization% gains, general TH04 progress would
be a very good investment.
The first push went to the often-mentioned stage-specific custom entities
that share a single statically allocated buffer. Back in 2020, I
📝 wrongly claimed that these were a TH05 innovation,
but the system actually originated in TH04. Both games use a 26-byte
structure, but TH04 only allocates a 32-element array rather than TH05's
64-element one. The conclusions from back then still apply, but I also kept
wondering why these games used a static array for these entities to begin
with. You know what they call an area of memory that you can cleanly
repurpose for things? That's right, a heap!
And absolutely no one would mind one additional heap allocation at the start
of a stage, next to the ones for all the sprites and portraits.
However, we are still running in Real Mode with segmented memory. Accessing
anything outside a common data segment involves modifying segment registers,
which has a nonzero CPU cycle cost, and Turbo C++ 4.0J is terrible at
optimizing away the respective instructions. Does this matter? Probably not,
but you don't take "risks" like these if you're in a permanent
micro-optimization mindset…
In TH04, this system is used for:
Kurumi's symmetric bullet spawn rays, fired from her hands towards the left
and right edges of the playfield. These are rather infamous for being the
last thing you see before
📝 the Divide Error crash that can happen in ZUN's original build.
Capped to 6 entities.
The 4 📝 bits used in Marisa's Stage 4 boss
fight. Coincidentally also related to the rare Divide Error
crash in that fight.
Stage 4 Reimu's spinning orbs. Note how the game uses two different sets
of sprites just to have two different outline colors. This was probably
better than messing with the palette, which can easily cause unintended
effects if you only have 16 colors to work with. Heck, I have an entire blog post tag just to highlight
these cases. Capped to the full 32 entities.
The chasing cross bullets, seen in Phase 14 of the same Stage 6 Yuuka
fight. Featuring some smart sprite work, making use of point symmetry to
achieve a fluid animation in just 4 frames. This is
good-code in sprite form. Capped to 31 entities, because the 32nd custom entity during this fight is defined to be…
The single purple pulsating and shrinking safety circle, seen in Phase 4 of
the same fight. The most interesting aspect here is actually still related
to the cross bullets, whose spawn function is wrongly limited to 32 entities
and could theoretically overwrite this circle. This
is strictly landmine territory though:
Yuuka never uses these bullets and the safety circle
simultaneously
She never spawns more than 24 cross bullets
All cross bullets are fast enough to have left the screen by the
time Yuuka restarts the corresponding subpattern
The cross bullets spawn at Yuuka's center position, and assign its
Q12.4 coordinates to structure fields that the safety circle interprets
as raw pixels. The game does try to render the circle afterward, but
since Yuuka's static position during this phase is nowhere near a valid
pixel coordinate, it is immediately clipped.
The flashing lines seen in Phase 5 of the Gengetsu fight,
telegraphing the slightly random bullet columns.
These structures only took 1 push to reverse-engineer rather than the 2 I
needed for their TH05 counterparts because they are much simpler in this
game. The "structure" for Gengetsu's lines literally uses just a single X
position, with the remaining 24 bytes being basically padding. The only
minor bug I found on this shallow level concerns Marisa's bits, which are
clipped at the right and bottom edges of the playfield 16 pixels earlier
than you would expect:
The remaining push went to a bunch of smaller structures and functions:
The structure for the up to 2 "thick" (a.k.a. "Master Spark") lasers. Much
saner than the
📝 madness of TH05's laser system while being
equally customizable in width and duration.
The structure for the various monochrome 16×16 shapes in the background of
the Stage 6 Yuuka fight, drawn on top of the checkerboard.
The rendering code for the three falling stars in the background of Stage 5.
The effect here is entirely palette-related: After blitting the stage tiles,
the 📝 1bpp star image is ORed
into only the 4th VRAM plane, which is equivalent to setting the
highest bit in the palette color index of every pixel within the star-shaped
region. This of course raises the question of how the stage would look like
if it was fully illuminated:
The full tile map of TH04's Stage 5, in both dark and fully
illuminated views. Since the illumination effect depends on two
matching sets of palette colors that are distinguished by a single
bit, the illuminated view is limited to only 8 of the 16 colors. The
dark view, on the other hand, can freely use colors from the
illuminated set, since those are unaffected by the OR
operation.
Most code that modifies a stage's tile map, and directly specifies tiles via
their top-left offset in VRAM.
Thanks to code alignment reasons, this forced a much longer detour into the
.STD format loader. Nothing all too noteworthy there since we're still
missing the enemy script and spawn structures before we can call .STD
"reverse-engineered", but maybe still helpful if you're looking for an
overview of the format. Also features a buffer overflow landmine if a .STD
file happens to contain more than 32 enemy scripts… you know, the usual
stuff.
To top off the second push, we've got the vertically scrolling checkerboard
background during the Stage 6 Yuuka fight, made up of 32×32 squares. This
one deserves a special highlight just because of its needless complexity.
You'd think that even a performant implementation would be pretty simple:
Set the GRCG to TDW mode
Set the GRCG tile to one of the two square colors
Start with Y as the current scroll offset, and X
as some indicator of which color is currently shown at the start of each row
of squares
Iterate over all lines of the playfield, filling in all pixels that
should be displayed in the current color, skipping over the other ones
Count down Y for each line drawn
If Y reaches 0, reset it to 32 and flip X
At the bottom of the playfield, change the GRCG tile to the other color,
and repeat with the initial value of X flipped
The most important aspect of this algorithm is how it reduces GRCG state
changes to a minimum, avoiding the costly port I/O that we've identified
time and time again as one of the main bottlenecks in TH01. With just 2
state variables and 3 loops, the resulting code isn't that complex either. A
naive implementation that just drew the squares from top to bottom in a
single pass would barely be simpler, but much slower: By changing the GRCG
tile on every color, such an implementation would burn a low 5-digit number
of CPU cycles per frame for the 12×11.5-square checkerboard used in the
game.
And indeed, ZUN retained all important aspects of this algorithm… but still
implemented it all in ASM, with a ridiculous layer of x86 segment arithmetic
on top? Which blows up the complexity to 4 state
variables, 5 nested loops, and a bunch of constants in unusual units. I'm
not sure what this code is supposed to optimize for, especially with that
rather questionable register allocation that nevertheless leaves one of the
general-purpose registers unused. Fortunately,
the function was still decompilable without too many code generation hacks,
and retains the 5 nested loops in all their goto-connected
glory. If you want to add a checkerboard to your next PC-98
demo, just stick to the algorithm I gave above.
(Using a single XOR for flipping the starting X offset between 32 and 64
pixels is pretty nice though, I have to give him that.)
This makes for a good occasion to talk about the third and final GRCG mode,
completing the series I started with my previous coverage of the
📝 RMW and
📝 TCR modes. The TDW (Tile Data Write) mode
is the simplest of the three and just writes the 8×1 GRCG tile into VRAM
as-is, without applying any alpha bitmask. This makes it perfect for
clearing rectangular areas of pixels – or even all of VRAM by doing a single
memset():
// Set up the GRCG in TDW mode.
outportb(0x7C, 0x80);
// Fill the tile register with color #7 (0111 in binary).
outportb(0x7E, 0xFF); // Plane 0: (B): (********)
outportb(0x7E, 0xFF); // Plane 1: (R): (********)
outportb(0x7E, 0xFF); // Plane 2: (G): (********)
outportb(0x7E, 0x00); // Plane 3: (E): ( )
// Set the 32 pixels at the top-left corner of VRAM to the exact contents of
// the tile register, effectively repeating the tile 4 times. In TDW mode, the
// GRCG ignores the CPU-supplied operand, so we might as well just pass the
// contents of a register with the intended width. This eliminates useless load
// instructions in the compiled assembly, and even sort of signals to readers
// of this code that we do not care about the source value.
*reinterpret_cast<uint32_t far *>(MK_FP(0xA800, 0)) = _EAX;
// Fill the entirety of VRAM with the GRCG tile. A simple C one-liner that will
// probably compile into a single `REP STOS` instruction. Unfortunately, Turbo
// C++ 4.0J only ever generates the 16-bit `REP STOSW` here, even when using
// the `__memset__` intrinsic and when compiling in 386 mode. When targeting
// that CPU and above, you'd ideally want `REP STOSD` for twice the speed.
memset(MK_FP(0xA800, 0), _AL, ((640 / 8) * 400));
However, this might make you wonder why TDW mode is even necessary. If it's
functionally equivalent to RMW mode with a CPU-supplied bitmask made up
entirely of 1 bits (i.e., 0xFF, 0xFFFF, or
0xFFFFFFFF), what's the point? The difference lies in the
hardware implementation: If all you need to do is write tile data to
VRAM, you don't need the read and modify parts of RMW mode
which require additional processing time. The PC-9801 Programmers'
Bible claims a speedup of almost 2× when using TDW mode over equivalent
operations in RMW mode.
And that's the only performance claim I found, because none of these old
PC-98 hardware and programming books did any benchmarks. Then again, it's
not too interesting of a question to benchmark either, as the byte-aligned
nature of TDW blitting severely limits its use in a game engine anyway.
Sure, maybe it makes sense to temporarily switch from RMW to TDW mode
if you've identified a large rectangular and byte-aligned section within a
sprite that could be blitted without a bitmask? But the necessary
identification work likely nullifies the performance gained from TDW mode,
I'd say. In any case, that's pretty deep
micro-optimization territory. Just use TDW mode for the
few cases it's good at, and stick to RMW mode for the rest.
So is this all that can be said about the GRCG? Not quite, because there are
4 bits I haven't talked about yet…
And now we're just 5.37% away from 100% position independence for TH04! From
this point, another 2 pushes should be enough to reach this goal. It might
not look like we're that close based on the current estimate, but a
big chunk of the remaining numbers are false positives from the player shot
control functions. Since we've got a very special deadline to hit, I'm going
to cobble these two pushes together from the two current general
subscriptions and the rest of the backlog. But you can, of course, still
invest in this goal to allow the existing contributions to go to something
else.
… Well, if the store was actually open. So I'd better
continue with a quick task to free up some capacity sooner rather than
later. Next up, therefore: Back to TH02, and its item and player systems.
Shouldn't take that long, I'm not expecting any surprises there. (Yeah, I
know, famous last words…)
Stripe is now
properly integrated into this website as an alternative to PayPal! Now, you
can also financially support the project if PayPal doesn't work for you, or
if you prefer using a
provider out of Stripe's greater variety. It's unfortunate that I had to
ship this integration while the store is still sold out, but the Shuusou
Gyoku OpenGL backend has turned out way too complicated to be finished next
to these two pushes within a month. It will take quite a while until the
store reopens and you all can start using Stripe, so I'll just link back to
this blog post when it happens.
Integrating Stripe wasn't the simplest task in the world either. At first,
the Checkout API
seems pretty friendly to developers: The entire payment flow is handled on
the backend, in the server language of your choice, and requires no frontend
JavaScript except for the UI feedback code you choose to write. Your
backend API endpoint initiates the Stripe Checkout session, answers with a
redirect to Stripe, and Stripe then sends a redirect back to your server if
the customer completed the payment. Superficially, this server-based
approach seems much more GDPR-friendly than PayPal, because there are no
remote scripts to obtain consent for. In reality though, Stripe shares
much more potential personal data about your credit card or bank
account with a merchant, compared to PayPal's almost bare minimum of
necessary data.
It's also rather annoying how the backend has to persist the order form
information throughout the entire Checkout session, because it would
otherwise be lost if the server restarts while a customer is still busy
entering data into Stripe's Checkout form. Compare that to the PayPal
JavaScript SDK, which only POSTs back to your server after the
customer completed a payment. In Stripe's case, more JavaScript actually
only makes the integration harder: If you trigger the initial payment
HTTP request from JavaScript, you will have
to improvise a bit to avoid the CORS error when redirecting away to a
different domain.
But sure, it's all not too bad… for regular orders at least. With
subscriptions, however, things get much worse. Unlike PayPal, Stripe
kind of wants to stay out of the way of the payment process as much as
possible, and just be a wrapper around its supported payment methods. So if
customers aren't really meant to register with Stripe, how would they cancel
their subscriptions?
Answer: Through
the… merchant? Which I quite dislike in principle, because why should
you have to trust me to actually cancel your subscription after you
requested it? It also means that I probably should add some sort of UI for
self-canceling a Stripe subscription, ideally without adding full-blown user
accounts. Not that this solves the underlying trust issue, but it's more
convenient than contacting me via email or, worse, going through your bank
somehow. Here is how my solution works:
When setting up a Stripe subscription, the server will generate a random
ID for authentication. This ID is then used as a salt for a hash
of the Stripe subscription ID, linking the two without storing the latter on
my server.
The thank you page, which is parameterized with the Stripe
Checkout session ID, will use that ID to retrieve the subscription
ID via an API call to Stripe, and display it together with the above
salt. This works indefinitely – contrary to what the expiry field in the
Checkout session object suggests, Stripe sessions are indeed stored
forever. After all, Stripe also displays this session information in a
merchant's transaction log with an excessive amount of detail. It might have
been better to add my own expiration system to these pages, but this had
been taking long enough already. For now, be aware that sharing the link to
a Stripe thank you page is equivalent to sharing your subscription
cancellation password.
The salt is then used as the key for a subscription management page. To
cancel, you visit this page and enter the Stripe subscription ID to confirm.
The server then checks whether the salt and subscription ID pair belong to
each other, and sends the actual cancellation
request back to Stripe if they do.
I might have gone a bit overboard with the crypto there, but I liked the
idea of not storing any of the Stripe session IDs in the server database.
It's not like that makes the system more complex anyway, and it's nice to
have a separate confirmation step before canceling a subscription.
But even that wasn't everything I had to keep in mind here. Once you
switch from test to production mode for the final tests, you'll notice that
certain SEPA-based
payment providers take their sweet time to process and activate new
subscriptions. The Checkout session object even informs you about that, by
including a payment status field. Which initially seems just like
another field that could indicate hacking attempts, but treating it as such
and rejecting any unpaid session can also reject perfectly valid
subscriptions. I don't want all this control… 🥲
Instead, all I can do in this case is to tell you about it. In my test, the
Stripe dashboard said that it might take days or even weeks for the initial
subscription transaction to be confirmed. In such a case, the respective
fraction of the cap will unfortunately need to remain red for that entire time.
And that was 1½ pushes just to replicate the basic functionality of a simple
PayPal integration with the simplest type of Stripe integration. On the
architectural site, all the necessary refactoring work made me finally
upgrade my frontend code to TypeScript at least, using the amazing esbuild to handle transpilation inside
the server binary. Let's see how long it will now take for me to upgrade to
SCSS…
With the new payment options, it makes sense to go for another slight price
increase, from up to per push.
The amount of taxes I have to pay on this income is slowly becoming
significant, and the store has been selling out almost immediately for the
last few months anyway. If demand remains at the current level or even
increases, I plan to gradually go up to by the end
of the year. 📝 As📝 usual,
I'm going to deliver existing orders in the backlog at the value they were
originally purchased at. Due to the way the cap has to be calculated, these
contributions now appear to have increased in value by a rather awkward
13.33%.
This left ½ of a push for some more work on the TH01 Anniversary Edition.
Unfortunately, this was too little time for the grand issue of removing
byte-aligned rendering of bigger sprites, which will need some additional
blitting performance research. Instead, I went for a bunch of smaller
bugfixes:
ANNIV.EXE now launches ZUNSOFT.COM if
MDRV98 wasn't resident before. In hindsight, it's completely obvious
why this is the right thing to do: Either you start
ANNIV.EXE directly, in which case there's no resident
MDRV98 and you haven't seen the ZUN Soft logo, or you have
made a single-line edit to GAME.BAT and replaced
op with anniv, in which case MDRV98 is
resident and you have seen the logo. These are the two
reasonable cases to support out of the box. If you are doing
anything else, it shouldn't be that hard to adjust though?
You might be wondering why I didn't just include all code of
ZUNSOFT.COM inside ANNIV.EXE together with
the rest of the game. The reason: ZUNSOFT.COM has
almost nothing in common with regular TH01 code. While the rest of
TH01 uses the custom image formats and bad rendering code I
documented again and again during its RE process,
ZUNSOFT.COM fully relies on master.lib for everything
about the bouncing-ball logo animation. Its code is much closer to
TH02 in that respect, which suggests that ZUN did in fact write this
animation for TH02, and just included the binary in TH01 for
consistency when he first sold both games together at Comiket 52.
Unlike the 📝 various bad reasons for splitting the PC-98 Touhou games into three main executables,
it's still a good idea to split off animations that use a completely
different set of rendering and file format functions. Combined with
all the BFNT and shape rendering code, ZUNSOFT.COM
actually contains even more unique code than OP.EXE,
and only slightly less than FUUIN.EXE.
The optional AUTOEXEC.BAT is now correctly encoded in
Shift-JIS instead of accidentally being UTF-8, fixing the previous
mojibake in its final ECHO line.
The command-line option that just adds a stage selection without
other debug features (anniv s) now works reliably.
This one's quite interesting because it only ever worked
because of a ZUN bug. From a superficial look at the code, it
shouldn't: While the presence of an 's' branch proves
that ZUN had such a mode during development, he nevertheless forgot
to initialize the debug flag inside the resident structure within
this branch. This mode only ever worked because master.lib's
resdata_create() function doesn't clear the resident
structure after allocation. If anything on the system previously
happened to write something other than 0x00,
0x01, or 0x03 to the specific byte that
then gets repurposed as the debug mode flag, this lack of
initialization does in fact result in a distinct non-test and
non-debug stage selection mode.
This is what happens on a certain widely circulated .HDI copy of
TH01 that boots MS-DOS 3.30C. On this system, the memory that
master.lib will allocate to the TH01 resident structure was
previously used by DOS as stack for its kernel, which left the
future resident debug flag byte at address 9FF6:0012 at
a value of 0x12. This might be the entire reason why
game s is even widely documented to trigger a stage
selection to begin with – on the widely circulated TH04 .HDI that
boots MS-DOS 6.20, or on DOSBox-X, the s parameter
doesn't work because both DOS systems leave the resident debug flag
byte at 0x00. And since ANNIV.EXE pushes
MDRV98 into that area of conventional DOS RAM, anniv s
previously didn't work even on MS-DOS 3.30C.
Both bugs in the
📝 1×1 particle system during the Mima fight
have been fixed. These include the off-by-one error that killed off the
very first particle on the 80th
frame and left it in VRAM, and, just like every other entity type, a
replacement of ZUN's EGC unblitter with the new pixel-perfect and fast
one. Until I've rearchitected unblitting as a whole, the particles will
now merely rip barely visible 1×1 holes into the sprites they overlap.
The bomb value shown in the lowest line of the in-game
debug mode output is now right-aligned together with the rest of the
values. This ensures that the game always writes a consistent number
of characters to TRAM, regardless of the magnitude of the
bomb value, preventing the seemingly wrong
timer values that appeared in the original game
whenever the value of the bomb variable changed to a
lower number of digits:
Finally, I've streamlined VRAM page access changes, which allowed me to
consistently replace ZUN's expensive function call with the optimal two
inlined x86 instructions. Interestingly, this change alone removed
2 KiB from the binary size, which is almost all of the difference
between 📝 the P0234-1 release and this
one. Let's see how much longer we can make each new release of
ANNIV.EXE smaller than the previous one.
The final point, however, raised the question of what we're now going to do
about
📝 a certain issue in the 地獄/Jigoku Bad Ending.
ZUN's original expensive way of switching the accessed VRAM page was the
main reason behind the lag frames on slower PC-98 systems, and
search-replacing the respective function calls would immediately get us to
the optimized version shown in that blog post. But is this something we
actually want? If we wanted to retain the lag, we could surely preserve that
function just for this one instance… The discovery of this issue
predates the clear distinction between bloat, quirks, and bugs, so it makes
sense to first classify what this issue even is. The distinction comes all
down to observability, which I defined as changes to rendered frames
between explicitly defined frame boundaries. That alone would be enough to
categorize any cause behind lag frames as bloat, but it can't hurt to be
more explicit here.
Therefore, I now officially judge observability in terms of an infinitely
fast PC-98 that can instantly render everything between two explicitly
defined frames, and will never add additional lag frames. If we plan to port
the games to faster architectures that aren't bottlenecked by disappointing
blitter chips, this is the only reasonable assumption to make, in my
opinion: The minimum system requirements in the games' README files are
minimums, after all, not recommendations. Chasing the exact frame
drop behavior that ZUN must have experienced during the time he developed
these games can only be a guessing game at best, because how can we know
which PC-98 model ZUN actually developed the games on? There might even be
more than one model, especially when it comes to TH01 which had been in
development for at least two years before ZUN first sold it. It's also not
like any current PC-98 emulator even claims to emulate the specific timing
of any existing model, and I sure hope that nobody expects me to import a
bunch of bulky obsolete hardware just to count dropped frames.
That leaves the tearing, where it's much more obvious how it's a bug. On an
infinitely fast PC-98, the ドカーン
frame would never be visible, and thus falls into the same category as the
📝 two unused animations in the Sariel fight.
With only a single unconditional 2-frame delay inside the animation loop, it
becomes clear that ZUN intended both frames of the animation to be displayed
for 2 frames each:
No tearing, and 34 frames in total for the first of the two
instances of this animation.
Next up: Taking the oldest still undelivered push and working towards TH04
position independence in preparation for multilingual translations. The
Shuusou Gyoku OpenGL backend shouldn't take that much longer either,
so I should have lots of stuff coming up in May afterward.
> "OK, TH03/TH04/TH05 cutscenes done, let's quickly finish the Touhou Patch Center MediaWiki upgrade. Just some scripting and verification left, it will be done so quickly that I don't even have to mention it on this blog"
> Still not done after 3 weeks
> Blocked by one final critical bug that really should be fixed upstream
> Code reviewers are probably on vacation
And so, the year unfortunately ended with yet another slow month. During the
MediaWiki upgrade, I was slowly decompiling the TH05 Sara fight on the side,
but stumbled over one interesting but high-maintenance detail there that
would really enhance her blog post. TH02 would need a lot of attention for
the basic rendering calls as well…
…so let's end the year with Shuusou Gyoku instead, looking at its most
critical issue in particular. As if that were the easy option here…
The game does not run properly on modern Windows systems due to its usage of
the ancient DirectDraw APIs, with issues ranging from unbearable slowdown to
glitched colors to the game not even starting at all. Thankfully, Shuusou
Gyoku is not the only ancient Windows game affected by these issues, and
people have developed a variety of generic DirectDraw wrappers and patches
for playing such games on modern systems. Out of all these, DDrawCompat is one of the
simpler solutions for Shuusou Gyoku in particular: Just drop its
ddraw proxy DLL into the game directory, and the game will run
as it's supposed to.
So let's just bundle that DLL with all my future Shuusou Gyoku releases
then? That would have been the quick and dirty option, coming with
several drawbacks:
Linux users might be annoyed by the potential need to configure a native
DLL override for ddraw.dll. It's not too much of an issue as we
could simply rename the DLL and replace the import with the new name.
However, doing that reproducibly would already involve changes to either the
DDrawCompat or Shuusou Gyoku build process.
Win32 API hooking is another potential point of failure in general,
requiring continual maintenance for new Windows versions. This is not even a
hypothetical concern: DDrawCompat does rely on particularly volatile Win32
API details, to the point that the recent Windows 11 22H2 update completely
broke it, causing a hang at startup that required a workaround.
But sure, it's still just a single third-party component. Keeping it up to
date doesn't sound too bad by itself…
…if DDrawCompat weren't evolving way beyond what we need to keep Shuusou
Gyoku running. Being a typical DirectDraw wrapper, it has always aimed to
solve all sorts of issues in old DirectDraw games. However, the latest
version, 0.4.0, has gone above and beyond in this regard, adding lots of
configuration options with default settings that actually
break Shuusou Gyoku.
To get a glimpse of how this is likely to play out, we only have to look at
the more mature DxWnd
project. In its expert mode, DxWnd features three rows of tabs, each packed
with checkboxes that toggle individual hacks, and most of these are
related to something that Shuusou Gyoku could be affected by. Imagine
checking a precise permutation of a three-digit number of checkboxes just to
keep an old game running at full speed on modern systems…
Finally, aesthetic and bloat considerations. If
📝 C++ fstreams were already too embarrassing
with the ~100 KB of bloat they add to the binary, a 565 KiB DLL is
even worse. And that's the old version 0.3.2 – version 0.4.0 comes in
at 2.43 MiB.
Fortunately, I had the budget to dig a bit deeper and figure out what
exactly DDrawCompat does to make Shuusou Gyoku work properly. Turns
out that among all the hooks and patches, the game only needs the most
central one: Enforcing a 32-bit display mode regardless of whatever lower
bit depth the game requests natively, combined with converting the game's
pixel buffer to 32-bit on the fly.
So does this mean that adding 32-bit to the game's list of supported bit
depths is everything we have to do?
Interestingly, Shuusou Gyoku already saved the DirectDraw enumeration flag
that indicates support for 32-bit display modes. The official version just
did nothing with it.
Well, almost everything. Initially, this surprised me as well: With
all the if statements checking for precise bit depths, you
would think that supporting one more bit depth would be way harder in this
code base. As it turned out though, these conditional branches are not
really about 8-bit or 16-bit color for the most part, but instead
differentiate between two very distinct rendering approaches:
"8-bit" is a pure 2D mode with palettized colors,
while "16-bit" is a hybrid 2D/3D mode that uses Direct3D 2 on top of DirectDraw, with
3-channel RGB colors.
Consequently, most of these branches deal with differences between these two
approaches that couldn't be nicely abstracted away in pbg's renderer
interface: Specific palette changes that are exclusive to "8-bit" mode, or
certain entities and effects whose Direct3D draw calls in "16-bit" mode
require tailor-made approximations for the "8-bit" mode. Since our new
32-bit mode is equivalent to the 16-bit mode in all of these branches, I
only needed to replace the raw number comparisons with more meaningful
method calls.
That only left a very small number of 2D raster effects that directly write
to or read from DirectDraw surface memory, and therefore do need to know the
bit size of each pixel. Thanks to std::variant and
std::visit(), adding 32-bit support becomes trivial here: By
rewriting the code in a generic manner that derives all offsets from the
template type, you only have to say hey,
I'd like to have 32-bit as well, and C++ will automatically
instantiate correct 32-bit variants of all bit depth-dependent code
snippets.
There are only three features in the entire game that access pixel buffers
this way: a color key retrieval function, the lens ball animation on the
logo screen, and… the ending staff roll? Sure, the text sprites fade in and
out, but so does the picture next to it, using Direct3D alpha blending or
palette color ramping depending on the current rendering mode. Instead, the
only reason why these sprites directly access their pixel buffer is… an
unused and pretty wild spiral effect. 😮 It's still part of the code, and
only doesn't show up because the
parameters that control its timing were commented out before release:
They probably considered it too wild for the mood of this
ending.
The main ending text was the only remaining issue of mojibake present in my
previous Shuusou Gyoku builds, and is now fixed as well. Windows can
render Shift-JIS text via GDI even outside Japanese locale, but only when
explicitly selecting a font that supports the SHIFTJIS_CHARSET,
and the game simply didn't select any font for rendering this text.
Thus, GDI fell back onto its default font, which obviously is only
guaranteed to support the SHIFTJIS_CHARSET if your system
locale is set to Japanese. This is why the font in the original game might
lookdifferent between systems.
For my build, I chose the font that would appear on a clean Windows
installation – a basic 400-weighted MS Gothic at font size 16, which is
already used all throughout the game.
Alright, 32-bit mode complete, let's set it as the default if possible… and
break compatibility to the original 秋霜CFG.DAT format in the
process? When validating this file, the original game only allows the
originally supported 8-bit or 16-bit modes. Setting the
BitDepth field to any other value causes the entire file
to be reset to its defaults, re-locking the Extra Stage in the process.
Introducing a backward-compatible version
system for 秋霜CFG.DAT was beyond the scope of this push.
Changing the validation to a per-field approach was a good small first step
to take though. The new build no longer validates the BitDepth
field against a fixed list, but against the actually supported bit depths on
your system, picking a different supported one if necessary. With the
original approach, this would have caused your entire configuration to fail
the validation check. Instead, you can now safely update to the new build
without losing your option settings, or your previously unlocked access to
the Extra Stage.
Side note: The validation limit for starting bombs is off by one, and the
one for starting lives check is off by two. By modifying
秋霜CFG.DAT, you could theoretically get new games to start with
7 lives and 3 bombs… if you then calculate a correct checksum for your
hacked config file, that is. 🧑💻
Interestingly, DirectDraw doesn't even indicate support for 8-bit or 16-bit
color on systems that are affected by the initially mentioned issues.
Therefore, these issues are not the fault of DirectDraw, but of
Shuusou Gyoku, as the original release requested a bit depth that it has
even verified to be unsupported. Unfortunately, Windows sides with
Sim City Shuusou Gyoku here: If you previously experimented with the
Windows app compatibility settings, you might have ended up with the
DWM8And16BitMitigation flag assigned to the full file path of
your Shuusou Gyoku executable in either
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers, or
As the term mitigation suggests, these modes are (poorly) emulated,
which is exactly what causes the issues with this game in the first place.
Sure, this might be the lesser evil from the point of view of an operating
system: If you don't have the budget for a full-blown DDrawCompat-style
DirectDraw wrapper, you might consider it better for users to have the game
run poorly than have it fail at startup due to incorrect API usage.
Controlling this with a flag that sticks around for future runs of a binary
is definitely suboptimal though, especially given how hard it
is to programmatically remove this flag within the binary itself. It
only adds additional complexity to the ideal clean upgrade path.
So, make sure to check your registry and manually remove these flags for the
time being. Without them, the new Config → Graphic menu will
correctly prevent you from selecting anything else but 32-bit on modern
Windows.
After all that, there was just enough time left in this push to implement
basic locale independence, as requested by the Seihou development
Discord group, without looking into automatic fixes for previous mojibake
filenames yet. Combining std::filesystem::path with the native
Win32 API should be straightforward and bloat-free, especially with all the
abstractions I've been building, right?
Well, turns out that std::filesystem::path does not
actually meet my expectations. At least as long as it's not
constexpr-enabled, because you still get the unfortunate
conversion from narrow to wide encoding at runtime, even for globals with
static storage duration. That brings us back to writing our path abstraction
in terms of the regular std::string and
std::wstring containers, which at least allow us to enforce the
respective encoding at compile time. Even std::string_view only
adds to the complexity here, as its strings are never inherently
null-terminated, which is required by both the POSIX and Win32 APIs. Not to
mention dynamic filenames: C++20's std::format() would be the
obvious idiomatic choice here, but using it almost doubles the size
of the compiled binary… 🤮
In the end, the most bloat-free way of implementing C++ file I/O in 2023 is
still the same as it was 30 years ago: Call system APIs, roll a custom
abstraction that conditionally uses the L prefix, and pass
around raw pointers. And if you need a dynamic filename, just write the
dynamic characters into arrays at fixed positions. Just as PC-98 Touhou used
to do…
Oh, and the game's window also uses a Unicode title bar now.
And that's it for this push! Make sure to rename your configuration
(秋霜CFG.DAT), score (秋霜SC.DAT), and replay
(秋霜りぷ*.DAT) filenames if you were previously running the
game on a non-Japanese locale, and then grab the new build:
Next up: Starting the new year with all my plans hopefully working out for
once. TH05 Sara very soon, ZMBV code review afterward, low-hanging fruit of
the TH01 Anniversary Edition after that, and then kicking off TH02 with a
bunch of low-level blitting code.
More than three months without any reverse-engineering progress! It's been
way too long. Coincidentally, we're at least back with a surprising 1.25% of
overall RE, achieved within just 3 pushes. The ending script system is not
only more or less the same in TH04 and TH05, but actually originated in
TH03, where it's also used for the cutscenes before stages 8 and 9. This
means that it was one of the final pieces of code shared between three of
the four remaining games, which I got to decompile at roughly 3× the usual
speed, or ⅓ of the price.
The only other bargains of this nature remain in OP.EXE. The
Music Room is largely equivalent in all three remaining games as well, and
the sound device selection, ZUN Soft logo screens, and main/option menus are
the same in TH04 and TH05. A lot of that code is in the "technically RE'd
but not yet decompiled" ASM form though, so it would shift Finalized% more
significantly than RE%. Therefore, make sure to order the new
Finalization option rather than Reverse-engineering if you
want to make number go up.
So, cutscenes. On the surface, the .TXT files look simple enough: You
directly write the text that should appear on the screen into the file
without any special markup, and add commands to define visuals, music, and
other effects at any place within the script. Let's start with the basics of
how text is rendered, which are the same in all three games:
First off, the text area has a size of 480×64 pixels. This means that it
does not correspond to the tiled area painted into TH05's
EDBK?.PI images:
The yellow area is designated for character names.
Since the font weight can be customized, all text is rendered to VRAM.
This also includes gaiji, despite them ignoring the font weight
setting.
The system supports automatic line breaks on a per-glyph basis, which
move the text cursor to the beginning of the red text area. This might seem like a piece of long-forgotten
ancient wisdom at first, considering the absence of automatic line breaks in
Windows Touhou. However, ZUN probably implemented it more out of pure
necessity: Text in VRAM needs to be unblitted when starting a new box, which
is way more straightforward and performant if you only need to worry
about a fixed area.
The system also automatically starts a new (key press-separated) text
box after the end of the 4th line. However, the text cursor is
also unconditionally moved to the top-left corner of the yellow name
area when this happens, which is almost certainly not what you expect, given
that automatic line breaks stay within the red area. A script author might
as well add the necessary text box change commands manually, if you're
forced to anticipate the automatic ones anyway…
Due to ZUN forgetting an unblitting call during the TH05 refactoring of the
box background buffer, this feature is even completely broken in that game,
as any new text will simply be blitted on top of the old one:
Wait, why are we already talking about game-specific differences after
all? Also, note how the ⏎ animation appears one line below where you'd
expect it.
Overall, the system is geared toward exclusively full-width text. As
exemplified by the 2014 static English patches and the screenshots in this
blog post, half-width text is possible, but comes with a lot of
asterisks attached:
Each loop of the script interpreter starts by looking at the next
byte to distinguish commands from text. However, this step also skips
over every ASCII space and control character, i.e., every byte
≤ 32. If you only intend to display full-width glyphs anyway, this
sort of makes sense: You gain complete freedom when it comes to the
physical layout of these script files, and it especially allows commands
to be freely separated with spaces and line breaks for improved
readability. Still, enforcing commands to be separated exclusively by
line breaks might have been even better for readability, and would have
freed up ASCII spaces for regular text…
Non-command text is blindly processed and rendered two bytes at a
time. The rendering function interprets these bytes as a Shift-JIS
string, so you can use half-width characters here. While the
second byte can even be an ASCII 0x20 space due to the
parser's blindness, all half-width characters must still occur in pairs
that can't be interrupted by commands:
As a workaround for at least the ASCII space issue, you can replace
them with any of the unassigned
Shift-JIS lead bytes – 0x80, 0xA0, or
anything between 0xF0 and 0xFF inclusive.
That's what you see in all screenshots of this post that display
half-width spaces.
Finally, did you know that you can hold ESC to fast-forward
through these cutscenes, which skips most frame delays and reduces the rest?
Due to the blocking nature of all commands, the ESC key state is
only updated between commands or 2-byte text groups though, so it can't
interrupt an ongoing delay.
Superficially, the list of game-specific differences doesn't look too long,
and can be summarized in a rather short table:
It's when you get into the implementation that the combined three systems
reveal themselves as a giant mess, with more like 56 differences between the
games. Every single new weird line of code opened up
another can of worms, which ultimately made all of this end up with 24
pieces of bloat and 14 bugs. The worst of these should be quite interesting
for the general PC-98 homebrew developers among my audience:
The final official 0.23 release of master.lib has a bug in
graph_gaiji_put*(). To calculate the JIS X 0208 code point for
a gaiji, it is enough to ADD 5680h onto the gaiji ID. However,
these functions accidentally use ADC instead, which incorrectly
adds the x86 carry flag on top, causing weird off-by-one errors based on the
previous program state. ZUN did fix this bug directly inside master.lib for
TH04 and TH05, but still needed to work around it in TH03 by subtracting 1
from the intended gaiji ID. Anyone up for maintaining a bug-fixed master.lib
repository?
The worst piece of bloat comes from TH03 and TH04 needlessly
switching the visibility of VRAM pages while blitting a new 320×200 picture.
This makes it much harder to understand the code, as the mere existence of
these page switches is enough to suggest a more complex interplay between
the two VRAM pages which doesn't actually exist. Outside this visibility
switch, page 0 is always supposed to be shown, and page 1 is always used
for temporarily storing pixels that are later crossfaded onto page 0. This
is also the only reason why TH03 has to render text and gaiji onto both VRAM
pages to begin with… and because TH04 doesn't, changing the picture in the
middle of a string of text is technically bugged in that game, even though
you only get to temporarily see the new text on very underclocked PC-98
systems.
These performance implications made me wonder why cutscenes even bother with
writing to the second VRAM page anyway, before copying each crossfade step
to the visible one.
📝 We learned in June how costly EGC-"accelerated" inter-page copies are;
shouldn't it be faster to just blit the image once rather than twice?
Well, master.lib decodes .PI images into a packed-pixel format, and
unpacking such a representation into bitplanes on the fly is just about the
worst way of blitting you could possibly imagine on a PC-98. EGC inter-page
copies are already fairly disappointing at 42 cycles for every 16 pixels, if
we look at the i486 and ignore VRAM latencies. But under the same
conditions, packed-pixel unpacking comes in at 81 cycles for every 8
pixels, or almost 4× slower. On lower-end systems, that can easily sum up to
more than one frame for a 320×200 image. While I'd argue that the resulting
tearing could have been an acceptable part of the transition between two
images, it's understandable why you'd want to avoid it in favor of the
pure effect on a slower framerate.
Really makes me wonder why master.lib didn't just directly decode .PI images
into bitplanes. The performance impact on load times should have been
negligible? It's such a good format for
the often dithered 16-color artwork you typically see on PC-98, and
deserves better than master.lib's implementation which is both slow to
decode and slow to blit.
That brings us to the individual script commands… and yes, I'm going to
document every single one of them. Some of their interactions and edge cases
are not clear at all from just looking at the code.
Almost all commands are preceded by… well, a 0x5C lead byte.
Which raises the question of whether we should
document it as an ASCII-encoded \ backslash, or a Shift-JIS-encoded
¥ yen sign. From a gaijin perspective, it seems obvious that it's a
backslash, as it's consistently displayed as one in most of the editors you
would actually use nowadays. But interestingly, iconv
-f shift-jis -t utf-8 does convert any 0x5C
lead bytes to actual ¥ U+00A5 YEN SIGN code points
.
Ultimately, the distinction comes down to the font. There are fonts
that still render 0x5C as ¥, but mainly do so out
of an obvious concern about backward compatibility to JIS X 0201, where this
mapping originated. Unsurprisingly, this group includes MS Gothic/Mincho,
the old Japanese fonts from Windows 3.1, but even Meiryo and Yu
Gothic/Mincho, Microsoft's modern Japanese fonts. Meanwhile, pretty much
every other modern font, and freely licensed ones in particular, render this
code point as \, even if you set your editor to Shift-JIS. And
while ZUN most definitely saw it as a ¥, documenting this code
point as \ is less ambiguous in the long run. It can only
possibly correspond to one specific code point in either Shift-JIS or UTF-8,
and will remain correct even if we later mod the cutscene system to support
full-blown Unicode.
Now we've only got to clarify the parameter syntax, and then we can look at
the big table of commands:
Numeric parameters are read as sequences of up to 3 ASCII digits. This
limits them to a range from 0 to 999 inclusive, with 000 and
0 being equivalent. Because there's no further sentinel
character, any further digit from the 4th one onwards is
interpreted as regular text.
Filename parameters must be terminated with a space or newline and are
limited to 12 characters, which translates to 8.3 basenames without any
directory component. Any further characters are ignored and displayed as
text as well.
Each .PI image can contain up to four 320×200 pictures ("quarters") for
the cutscene picture area. In the script commands, they are numbered like
this:
0
1
2
3
\@
Clears both VRAM pages by filling them with VRAM color 0. 🐞
In TH03 and TH04, this command does not update the internal text area
background used for unblitting. This bug effectively restricts usage of
this command to either the beginning of a script (before the first
background image is shown) or its end (after no more new text boxes are
started). See the image below for an
example of using it anywhere else.
\b2
Sets the font weight to a value between 0 (raw font ROM glyphs) to 3
(very thicc). Specifying any other value has no effect.
🐞 In TH04 and TH05, \b3 leads to glitched pixels when
rendering half-width glyphs due to a bug in the newly micro-optimized
ASM version of
📝 graph_putsa_fx(); see the image below for an example.
In these games, the parameter also directly corresponds to the
graph_putsa_fx() effect function, removing the sanity check
that was present in TH03. In exchange, you can also access the four
dissolve masks for the bold font (\b2) by specifying a
parameter between 4 (fewest pixels) to 7 (most
pixels). Demo video below.
\c15
Changes the text color to VRAM color 15.
\c=字,15
Adds a color map entry: If 字 is the first code point
inside the name area on a new line, the text color is automatically set
to 15. Up to 8 such entries can be registered
before overflowing the statically allocated buffer.
🐞 The comma is assumed to be present even if the color parameter is omitted.
\e0
Plays the sound effect with the given ID.
\f
(no-op)
\fi1
\fo1
Calls master.lib's palette_black_in() or
palette_black_out() to play a hardware palette fade
animation from or to black, spending roughly 1 frame on each of the 16 fade steps.
\fm1
Fades out BGM volume via PMD's AH=02h interrupt call,
in a non-blocking way. The fade speed can range from 1 (slowest) to 127 (fastest).
Values from 128 to 255 technically correspond to
AH=02h's fade-in feature, which can't be used from cutscene
scripts because it requires BGM volume to first be lowered via
AH=19h, and there is no command to do that.
\g8
Plays a blocking 8-frame screen shake
animation.
\ga0
Shows the gaiji with the given ID from 0 to 255
at the current cursor position. Even in TH03, gaiji always ignore the
text delay interval configured with \v.
@3
TH05's replacement for the \ga command from TH03 and
TH04. The default ID of 3 corresponds to the
gaiji. Not to be confused with \@, which starts with a backslash,
unlike this command.
@h
Shows the gaiji.
@t
Shows the gaiji.
@!
Shows the gaiji.
@?
Shows the gaiji.
@!!
Shows the gaiji.
@!?
Shows the gaiji.
\k0
Waits 0 frames (0 = forever) for an advance key to be pressed before
continuing script execution. Before waiting, TH05 crossfades in any new
text that was previously rendered to the invisible VRAM page…
🐞 …but TH04 doesn't, leaving the text invisible during the wait time.
As a workaround, \vp1 can be
used before \k to immediately display that text without a
fade-in animation.
\m$
Stops the currently playing BGM.
\m*
Restarts playback of the currently loaded BGM from the
beginning.
\m,filename
Stops the currently playing BGM, loads a new one from the given
file, and starts playback.
\n
Starts a new line at the leftmost X coordinate of the box, i.e., the
start of the name area. This is how scripts can "change" the name of the
currently speaking character, or use the entire 480×64 pixels without
being restricted to the non-name area.
Note that automatic line breaks already move the cursor into a new line.
Using this command at the "end" of a line with the maximum number of 30
full-width glyphs would therefore start a second new line and leave the
previously started line empty.
If this command moved the cursor into the 5th line of a box,
\s is executed afterward, with
any of \n's parameters passed to \s.
\p
(no-op)
\p-
Deallocates the loaded .PI image.
\p,filename
Loads the .PI image with the given file into the single .PI slot
available to cutscenes. TH04 and TH05 automatically deallocate any
previous image, 🐞 TH03 would leak memory without a manual prior call to
\p-.
\pp
Sets the hardware palette to the one of the loaded .PI image.
\p@
Sets the loaded .PI image as the full-screen 640×400 background
image and overwrites both VRAM pages with its pixels, retaining the
current hardware palette.
\p=
Runs \pp followed by \p@.
\s0
\s-
Ends a text box and starts a new one. Fades in any text rendered to
the invisible VRAM page, then waits 0 frames
(0 = forever) for an advance key to be
pressed. Afterward, the new text box is started with the cursor moved to
the top-left corner of the name area. \s- skips the wait time and starts the new box
immediately.
\t100
Sets palette brightness via master.lib's
palette_settone() to any value from 0 (fully black) to 200
(fully white). 100 corresponds to the palette's original colors.
Preceded by a 1-frame delay unless ESC is held.
\v1
Sets the number of frames to wait between every 2 bytes of rendered
text.
Sets the number of frames to spend on each of the 4 fade
steps when crossfading between old and new text. The game-specific
default value is also used before the first use of this command.
\v2
\vp0
Shows VRAM page 0. Completely useless in
TH03 (this game always synchronizes both VRAM pages at a command
boundary), only of dubious use in TH04 (for working around a bug in \k), and the games always return to
their intended shown page before every blitting operation anyway. A
debloated mod of this game would just remove this command, as it exposes
an implementation detail that script authors should not need to worry
about. None of the original scripts use it anyway.
\w64
\w and \wk wait for the given number
of frames
\wm and \wmk wait until PMD has played
back the current BGM for the total number of measures, including
loops, given in the first parameter, and fall back on calling
\w and \wk with the second parameter as
the frame number if BGM is disabled.
🐞 Neither PMD nor MMD reset the internal measure when stopping
playback. If no BGM is playing and the previous BGM hasn't been
played back for at least the given number of measures, this command
will deadlock.
Since both TH04 and TH05 fade in any new text from the invisible VRAM
page, these commands can be used to simulate TH03's typing effect in
those games. Demo video below.
Contrary to \k and \s, specifying 0 frames would
simply remove any frame delay instead of waiting forever.
The TH03-exclusive k variants allow the delay to be
interrupted if ⏎ Return or Shot are held down.
TH04 and TH05 recognize the k as well, but removed its
functionality.
All of these commands have no effect if ESC is held.
\wm64,64
\wk64
\wmk64,64
\wi1
\wo1
Calls master.lib's palette_white_in() or
palette_white_out() to play a hardware palette fade
animation from or to white, spending roughly 1 frame on each of the 16 fade steps.
\=4
Immediately displays the given quarter of the loaded .PI image in
the picture area, with no fade effect. Any value ≥ 4 resets the picture area to black.
\==4,1
Crossfades the picture area between its current content and quarter
#4 of the loaded .PI image, spending 1 frame on each of the 4 fade steps unless
ESC is held. Any value ≥ 4 is
replaced with quarter #0.
\$
Stops script execution. Must be called at the end of each file;
otherwise, execution continues into whatever lies after the script
buffer in memory.
TH05 automatically deallocates the loaded .PI image, TH03 and TH04
require a separate manual call to \p- to not leak its memory.
Bold values signify the default if the parameter
is omitted; \c is therefore
equivalent to \c15.
The \@ bug. Yes, the ¥ is fake. It
was easier to GIMP it than to reword the sentences so that the backslashes
landed on the second byte of a 2-byte half-width character pair.
The font weights and effects available through \b, including the glitch with
\b3 in TH04 and TH05.
Font weight 3 is technically not rendered correctly in TH03 either; if
you compare 1️⃣ with 4️⃣, you notice a single missing column of pixels
at the left side of each glyph, which would extend into the previous
VRAM byte. Ironically, the TH04/TH05 version is more correct in
this regard: For half-width glyphs, it preserves any further pixel
columns generated by the weight functions in the high byte of the 16-dot
glyph variable. Unlike TH03, which still cuts them off when rendering
text to unaligned X positions (3️⃣), TH04 and TH05 do bit-rotate them
towards their correct place (4️⃣). It's only at byte-aligned X positions
(2️⃣) where they remain at their internally calculated place, and appear
on screen as these glitched pixel columns, 15 pixels away from the glyph
they belong to. It's easy to blame bugs like these on micro-optimized
ASM code, but in this instance, you really can't argue against it if the
original C++ version was equally incorrect.
Combining \b and s- into a partial dissolve
animation. The speed can be controlled with \v.
Simulating TH03's typing effect in TH04 and TH05 via \w. Even prettier in TH05 where we
also get an additional fade animation
after the box ends.
So yeah, that's the cutscene system. I'm dreading the moment I will have to
deal with the other command interpreter in these games, i.e., the
stage enemy system. Luckily, that one is completely disconnected from any
other system, so I won't have to deal with it until we're close to finishing
MAIN.EXE… that is, unless someone requests it before. And it
won't involve text encodings or unblitting…
The cutscene system got me thinking in greater detail about how I would
implement translations, being one of the main dependencies behind them. This
goal has been on the order form for a while and could soon be implemented
for these cutscenes, with 100% PI being right around the corner for the TH03
and TH04 cutscene executables.
Once we're there, the "Virgin" old-school way of static translation patching
for Latin-script languages could be implemented fairly quickly:
Establish basic UTF-8 parsing for less painful manual editing of the
source files
Procedurally generate glyphs for the few required additional letters
based on existing font ROM glyphs. For example, we'd generate ä
by painting two short lines on top of the font ROM's a glyph,
or generate ¿ by vertically flipping the question mark. This
way, the text retains a consistent look regardless of whether the translated
game is run with an NEC or EPSON font ROM, or the that Neko Project II auto-generates if you
don't provide either.
(Optional) Change automatic line breaks to work on a per-word
basis, rather than per-glyph
That's it – script editing and distribution would be handled by your local
translation group. It might seem as if this would also work for Greek and
Cyrillic scripts due to their presence in the PC-98 font ROM, but I'm not
sure if I want to attempt procedurally shrinking these glyphs from 16×16 to
8×16… For any more thorough solution, we'd need to go for a more "Chad" kind
of full-blown translation support:
Implement text subdivisions at a sensible granularity while retaining
automatic line and box breaks
Compile translatable text into a Japanese→target language dictionary
(I'm too old to develop any further translation systems that would overwrite
modded source text with translations of the original text)
Implement a custom Unicode font system (glyphs would be taken from GNU
Unifont unless translators provide a different 8×16 font for their
language)
Combine the text compiler with the font compiler to only store needed
glyphs as part of the translation's font file (dealing with a multi-MB font
file would be rather ugly in a Real Mode game)
Write a simple install/update/patch stacking tool that supports both
.HDI and raw-file DOSBox-X scenarios (it's different enough from thcrap to
warrant a separate tool – each patch stack would be statically compiled into
a single package file in the game's directory)
Add a nice language selection option to the main menu
(Optional) Support proportional fonts
Which sounds more like a separate project to be commissioned from
Touhou Patch Center's Open Collective funds, separate from the ReC98 cap.
This way, we can make sure that the feature is completely implemented, and I
can talk with every interested translator to make sure that their language
works.
It's still cheaper overall to do this on PC-98 than to first port the games
to a modern system and then translate them. On the other hand, most
of the tasks in the Chad variant (3, 4, 5, and half of 2) purely deal with
the difficulty of getting arbitrary Unicode characters to work natively in a
PC-98 DOS game at all, and would be either unnecessary or trivial if we had
already ported the game. Depending on where the patrons' interests lie, it
may not be worth it. So let's see what all of you think about which
way we should go, or whether it's worth doing at all. (Edit
(2022-12-01): With Splashman's
order towards the stage dialogue system, we've pretty much confirmed that it
is.) Maybe we want to meet in the middle – using e.g. procedural glyph
generation for dynamic translations to keep text rendering consistent with
the rest of the PC-98 system, and just not support non-Latin-script
languages in the beginning? In any case, I've added both options to the
order form. Edit (2023-07-28):Touhou Patch Center has agreed to fund
a basic feature set somewhere between the Virgin and Chad level. Check the
📝 dedicated announcement blog post for more
details and ideas, and to find out how you can support this goal!
Surprisingly, there was still a bit of RE work left in the third push after
all of this, which I filled with some small rendering boilerplate. Since I
also wanted to include TH02's playfield overlay functions,
1/15 of that last push went towards getting a
TH02-exclusive function out of the way, which also ended up including that
game in this delivery.
The other small function pointed out how TH05's Stage 5 midboss pops into
the playfield quite suddenly, since its clipping test thinks it's only 32
pixels tall rather than 64:
Good chance that the pop-in might have been intended. Edit (2023-06-30): Actually, it's a
📝 systematic consequence of ZUN having to work around the lack of clipping in master.lib's sprite functions.
There's even another quirk here: The white flash during its first frame
is actually carried over from the previous midboss, which the
game still considers as actively getting hit by the player shot that
defeated it. It's the regular boilerplate code for rendering a
midboss that resets the responsible damage variable, and that code
doesn't run during the defeat explosion animation.
Next up: Staying with TH05 and looking at more of the pattern code of its
boss fights. Given the remaining TH05 budget, it makes the most sense to
continue in in-game order, with Sara and the Stage 2 midboss. If more money
comes in towards this goal, I could alternatively go for the Mai & Yuki
fight and immediately develop a pretty fix for the cheeto storage
glitch. Also, there's a rather intricate
pull request for direct ZMBV decoding on the website that I've still got
to review…
On August 15, 1997, at Comiket 52, an unknown doujin developer going by the
name of ZUN released his first game, 東方靈異伝 ～
The Highly Responsive to Prayers, marking the start of the
Touhou Project game series that keeps running to this day. Today, exactly 25
years later, the C++ source code to version 1.10 of that game has been
completely and perfectly reconstructed, reviewed, and documented.
And with that, a warm welcome to all game journalists who have
(re-)discovered this project through these news! Here's a summary for
everyone who doesn't want to go through 3 years worth of blog posts:
What does this mean?
All code that ZUN wrote as part of a TH01 installation has now been
decompiled to C++ code. The only parts left in assembly are two third-party
libraries (master.lib and PiLoad), which were originally written in
assembly, and are built from their respective official source code.
You can clone the ReC98
repository, set up the build environment, and get a binary with an
identical program image. The hashes of the resulting executables won't match
those of ZUN's original release, but all differences there stem from details
in the .EXE header that don't influence program execution, such as the
on-disk order of the conceptually unordered set of x86 memory segment
relocations. If you're interested in that level of correctness, you can
order Easier verification against original binaries from the store.
For now though, use mzdiff for
verifying the builds against ZUN's binaries.
Ever since this crowdfunding has started 3 years ago, the goal of this
project has shifted more and more towards a full-on code review rather than
being just a mechanical decompilation:
Hardcoded constants were derived from as few truly hardcoded values
as possible, which uncovered their intended meaning and highlighted any
inconsistencies
Code was deduplicated to a perhaps obsessive level (I'm still trying
to find a balance)
Tons of comments everywhere to put everything into context
And, of course, 2½ years worth of blog
posts summarizing any highlights, glitches, and secrets. (There
might still be some left to be discovered!)
As a result, modding the games and porting them away from the PC-98
platform is now a lot easier.
What does this not mean?
This is not a piracy release. ReC98 only provides the code that the
game's .EXE and .COM files are built out of. Without the rest of the
original data files, supplied from a pre-existing game copy, the code won't
do very much.
Even apart from ZUN's own code quality, the ReC98 repository is not as
polished and consistent as it could be, having seen multiple code structure
evolutions over the 8 years of its existence.
TH01 hasn't magically reached Doom levels of easy portability now. As a
decompilation of the exact code that ZUN wrote for the PC-98 platform, it is
very PC-98-native, and wildly mixes game logic with hardware
accesses. As ZUN's first foray into game development, he understandably
didn't see the need for writing an engine or hardware abstraction layer
yet.
So while this milestone opened the floodgates to PC-98-native mods, I
wouldn't advise trying to attempt a port away from PC-98 right now. But then
again, I have a financial interest in being a part of the porting process,
and who knows, maybe you can just merge in a PC-98 emulator core and
get started with something halfway decent in a short amount of time. After
all, TH01 is by far the easiest PC-98 Touhou game to port to other systems,
as it makes the least use of hardware features. (Edit
(2023-03-30): 📝 Turns out that this
crown actually goes to TH02. It features the least amount of ZUN-written
PC-98-specific rendering code out of all the 5 games, with most of it
being decently abstracted via master.lib.)
However, this game in particular raises the question of what exactly
one would even want to port. TH01 is a broken flicker-fest that
overwhelmingly suffers the drawbacks of PC-98 hardware rather than using it
to its advantage. Out of the 78 bugs that I ended up labeling as such, the
majority are sprite blitting issues,
while you can count the instances of
good hardware use on one hand.
And even at the level of game logic, this game features a lot of
weird, inconsistent behavior. Less rigorous projects such as uth05win would probably
promptly identify these issues as bugs and fix them. On the one hand, this
shows that there is a part of the community that wants sane versions of
these games which behave as expected. In other parts of the community
though, such projects quickly gain the reputation of being too inaccurate to
bother about them.
Some terminology might help here. If you look over the ReC98 codebase,
you'll find that I classified any weird code into three categories.
Edit (2023-03-05): These have been overhauled with a new
landmine category for invisible issues. Check CONTRIBUTING.md
for the complete and current current definition of all weird code
categories.
🔗 ZUN bugs: Broken
code that results from logic errors or incorrect programming
language/API/hardware use, with enough evidence in the code to indicate that
ZUN did not intend the bug. Fixing these issues must not affect hypothetical
replay compatibility, and any resulting visual changes must match ZUN's
provable intentions.
🔗 ZUN quirks:
Weird code that looks incorrect in context. Fixing these issues would change
gameplay enough to desync a hypothetical replay recorded on the original
version, or affect the visuals so much that the result is no longer faithful
to ZUN's original release. It might very well be called a fangame at that
point.
🔗 ZUN bloat:
Code that wastes memory, CPU cycles, or even just the mental capacity of
anyone trying to read and understand the code. If you want to write a
particularly resource-intensive mod, these are the places you could claim
some of those resources from.
Some examples:
All crashes are bugs
All blitting issues related to inappropriate VRAM byte alignment are
bugs
The idea of splitting TH01 across three executables is its biggest
source of bloat. It wastes disk space, the game doesn't even make use of the
memory gained from unloading unneeded code and data, it complicates the
build process and code structure with inconsistencies between the individual
binaries, and the required inter-process communication via shared memory
adds another piece of global state mutation headache.
Since I'm not in the business of writing fanfiction, I won't offer any
option that fixes quirks. That's where all of you can come in, and
use ReC98 as a base for remasters and remakes. As for bloat and bugs though,
there are many ways we could go from here:
If you want to ultimately try porting the game yourself, but still
support ReC98 somehow, I can recommend the ZUN code cleanup goal.
This is the most conservative option that leaves all bugs and quirks in
place and only removes bloat, rearchitecting the codebase so that
it's easier to work with.
For an improved gameplay experience on PC-98, choose the TH01
Anniversary Edition goal. In addition to the above code cleanup, this
goal fixes every bug with the game, most notably all the sprite
flickering by implementing a completely new renderer, while maintaining
hypothetical replay compatibility to ZUN's original release.
If you're mainly interested in seeing any variety of TH01 ported away
from PC-98 to any system, choose the Portability to non-PC-98 systems
goal. In this one, I'm going to develop the abstraction layers that would
ultimately bring this game to the aforementioned Doom level of portability,
while still keeping it running with better than original performance on
PC-98.
Replay support is also something you could order…
… as is Multilingual translation support (on PC-98), for those
sweet non-ASCII characters if that's your thing.
Then again, with all these choices in mind, maybe we should just let TH01 be
what it is: ZUN's first game, evidence for the truth that no programmer
writes good code the first time around, and more of a historical curiosity
than anything you'd want to maintain and modernize. The idea of moving on to
the next game and decompiling all 5 PC-98 Touhou games in order has
certainly shown to be
popular among the backers who funded this 100% goal.
Since the beginning of the year, I've been dramatically raising the level of
quality and care I've been putting into this project, leading to 9 of the 10
longest blog posts having been written in the past 8 months. The community
reception has been even more supportive as well, with all of you still
regularly selling out the store in return. To match the level of quality
with the community demand, I'm raising push prices from
to per push, as of this blog
post. 📝 As usual, I'm going to deliver any
existing orders in the backlog at the value they were originally purchased
at. Due to the way the cap has to be calculated, these contributions now
appear to have increased in value by 25%.
However, I do realize that this might make regular pushes prohibitively
expensive for some. This could especially prevent all these exciting modding
goals from ever getting off the ground. Thinking about it though, the push
system is only really necessary for the core reverse-engineering business,
where longer, concentrated stretches of work allow me to study a new piece
of code in a larger context and improve the quality of the final result. In
contrast, modding-related goals could theoretically be segmented into
arbitrarily small portions of work, as I have a clear idea of where I want
to go and how to get there.
Thus, I'm introducing microtransactions, now available for all
modding-related goals. These allow you to order fractional pieces of work
for as low as 1 €, which I will immediately deliver without requiring others
to fund a full push first. Edit (2022-08-16): And then the
store still sold out with a single regular contribution by
nrook towards more reverse-engineering. Guess that this
experiment will have to wait a little while longer, then… 😅
Next up: Taking a break and recovering from crunch time by improving video
playback on this blog and working on Shuusou Gyoku,
before returning to Touhou in September.
Oh look, it's another rather short and straightforward boss with a rather
small number of bugs and quirks. Yup, contrary to the character's
popularity, Mima's premiere is really not all that special in terms of code,
and continues the trend established with
📝 Kikuri and
📝 SinGyoku. I've already covered
📝 the initial sprite-related bugs last November,
so this post focuses on the main code of the fight itself. The overview:
The TH01 Mima fight consists of 3 phases, with phases 1 and 3 each
corresponding to one half of the 12-HP bar.
📝 Just like with SinGyoku, the distinction
between the red-white and red parts is purely visual once again, and doesn't
reflect anything about the boss script. As usual, all of the phases have to
be completed in order.
Phases 1 and 3 cycle through 4 danmaku patterns each, for a total of 8.
The cycles always start on a fixed pattern.
3 of the patterns in each phase feature rotating white squares, thus
introducing a new sprite in need of being unblitted.
Phase 1 additionally features the "hop pattern" as the last one in its
cycle. This is the only pattern where Mima leaves the seal in the center of
the playfield to hop from one edge of the playfield towards the other, while
also moving slightly higher up on the Y axis, and staying on the final
position for the next pattern cycle. For the first time, Mima selects a
random starting edge, which is then alternated on successive cycles.
Since the square entities are local to the respective pattern function,
Phase 1 can only end once the current pattern is done, even if Mima's HP are
already below 6. This makes Mima susceptible to the
📝 test/debug mode HP bar heap corruption bug.
Phase 2 simply consists of a spread-in teleport back to Mima's initial
position in the center of the playfield. This would only have been strictly
necessary if phase 1 ended on the hop pattern, but is done regardless of the
previous pattern, and does provide a nice visual separation between the two
main phases.
That's it – nothing special in Phase 3.
And there aren't even any weird hitboxes this time. What is maybe
special about Mima, however, is how there's something to cover about all of
her patterns. Since this is TH01, it's won't surprise anyone that the
rotating square patterns are one giant copy-pasta of unblitting, updating,
and rendering code. At least ZUN placed the core polar→Cartesian
transformation in a separate function for creating regular polygons
with an arbitrary number of sides, which might hint toward some more varied
shapes having been planned at one point?
5 of the 6 patterns even follow the exact same steps during square update
frames:
Calculate square corner coordinates
Unblit the square
Update the square angle and radius
Use the square corner coordinates for spawning pellets or missiles
Recalculate square corner coordinates
Render the square
Notice something? Bullets are spawned before the corner coordinates
are updated. That's why their initial positions seem to be a bit off – they
are spawned exactly in the corners of the square, it's just that it's
the square from 8 frames ago.
Mima's first pattern on Normal difficulty.
Once ZUN reached the final laser pattern though, he must have noticed that
there's something wrong there… or maybe he just wanted to fire those
lasers independently from the square unblit/update/render timer for a
change. Spending an additional 16 bytes of the data segment for conveniently
remembering the square corner coordinates across frames was definitely a
decent investment.
When Mima isn't shooting bullets from the corners of a square or hopping
across the playfield, she's raising flame pillars from the bottom of the playfield within very specifically calculated
random ranges… which are then rendered at byte-aligned VRAM positions, while
collision detection still uses their actual pixel position. Since I don't
want to sound like a broken record all too much, I'll just direct you to
📝 Kikuri, where we've seen the exact same issue with the teardrop ripple sprites.
The conclusions are identical as well.
Mima's flame pillar pattern. This video was recorded on a particularly
unlucky seed that resulted in great disparities between a pillar's
internal X coordinate and its byte-aligned on-screen appearance, leading
to lots of right-shifted hitboxes.
Also note how the change from the meteor animation to the three-arm 🚫
casting sprite doesn't unblit the meteor, and leaves that job to
any sprite that happens to fly over those pixels.
However, I'd say that the saddest part about this pattern is how choppy it
is, with the circle/pillar entities updating and rendering at a meager 7
FPS. Why go that low on purpose when you can just make the game render ✨
smoothly ✨ instead?
So smooth it's almost uncanny.
The reason quickly becomes obvious: With TH01's lack of optimization, going
for the full 56.4 FPS would have significantly slowed down the game on its
intended 33 MHz CPUs, requiring more than cheap surface-level ASM
optimization for a stable frame rate. That might very well have been ZUN's
reason for only ever rendering one circle per frame to VRAM, and designing
the pattern with these time offsets in mind. It's always been typical for
PC-98 developers to target the lowest-spec models that could possibly still
run a game, and implementing dynamic frame rates into such an engine-less
game is nothing I would wish on anybody. And it's not like TH01 is
particularly unique in its choppiness anyway; low frame rates are actually a
rather typical part of the PC-98 game aesthetic.
The final piece of weirdness in this fight can be found in phase 1's hop
pattern, and specifically its palette manipulation. Just from looking at the
pattern code itself, each of the 4 hops is supposed to darken the hardware
palette by subtracting #444 from every color. At the last hop,
every color should have therefore been reduced to a pitch-black
#000, leaving the player completely blind to the movement of
the chasing pellets for 30 frames and making the pattern quite ghostly
indeed. However, that's not what we see in the actual game:
Nothing in the pattern's code would cause the hardware palette to get
brighter before the end of the pattern, and yet…
The expected version doesn't look all too unfair, even on Lunatic…
well, at least at the default rank pellet speed shown in this
video. At maximum pellet speed, it is in fact rather brutal.
Looking at the frame counter, it appears that something outside the
pattern resets the palette every 40 frames. The only known constant with a
value of 40 would be the invincibility frames after hitting a boss with the
Orb, but we're not hitting Mima here…
But as it turns out, that's exactly where the palette reset comes from: The
hop animation darkens the hardware palette directly, while the
📝 infamous 12-parameter boss collision handler function
unconditionally resets the hardware palette to the "default boss palette"
every 40 frames, regardless of whether the boss was hit or not. I'd classify
this as a bug: That function has no business doing periodic hardware palette
resets outside the invincibility flash effect, and it completely defies
common sense that it does.
That explains one unexpected palette change, but could this function
possibly also explain the other infamous one, namely, the temporary green
discoloration in the Konngara fight? That glitch comes down to how the game
actually uses two global "default" palettes: a default boss
palette for undoing the invincibility flash effect, and a default
stage palette for returning the colors back to normal at the end of
the bomb animation or when leaving the Pause menu. And sure enough, the
stage palette is the one with the green color, while the boss
palette contains the intended colors used throughout the fight. Sending the
latter palette to the graphics chip every 40 frames is what corrects
the discoloration, which would otherwise be permanent.
The green color comes from BOSS7_D1.GRP, the scrolling
background of the entrance animation. That's what turns this into a clear
bug: The stage palette is only set a single time in the entire fight,
at the beginning of the entrance animation, to the palette of this image.
Apart from consistency reasons, it doesn't even make sense to set the stage
palette there, as you can't enter the Pause menu or bomb during a blocking
animation function.
And just 3 lines of code later, ZUN loads BOSS8_A1.GRP, the
main background image of the fight. Moving the stage palette assignment
there would have easily prevented the discoloration.
But yeah, as you can tell, palette manipulation is complete jank in this
game. Why differentiate between a stage and a boss palette to begin with?
The blocking Pause menu function could have easily copied the original
palette to a local variable before darkening it, and then restored it after
closing the menu. It's not so easy for bombs as the intended palette could
change between the start and end of the animation, but the code could have
still been simplified a lot if there was just one global "default palette"
variable instead of two. Heck, even the other bosses who manipulate their
palettes correctly only do so because they manually synchronize the two
after every change. The proper defense against bugs that result from wild
mutation of global state is to get rid of global state, and not to put up
safety nets hidden in the middle of existing effect code.
The easiest way of reproducing the green discoloration bug in
the TH01 Konngara fight, timed to show the maximum amount of time the
discoloration can possibly last.
In any case, that's Mima done! 7th PC-98 Touhou boss fully
decompiled, 24 bosses remaining, and 59 functions left in all of TH01.
In other thrilling news, my call for secondary funding priorities in new
TH01 contributions has given us three different priorities so far. This
raises an interesting question though: Which of these contributions should I
now put towards TH01 immediately, and which ones should I leave in the
backlog for the time being? Since I've never liked deciding on priorities,
let's turn this into a popularity contest instead: The contributions with
the least popular secondary priorities will go towards TH01 first, giving
the most popular priorities a higher chance to still be left over after TH01
is done. As of this delivery, we'd have the following popularity order:
TH05 (1.67 pushes), from T0182
Seihou (1 push), from T0184
TH03 (0.67 pushes), from T0146
Which means that T0146 will be consumed for TH01 next, followed by T0184 and
then T0182. I only assign transactions immediately before a delivery though,
so you all still have the chance to change up these priorities before the
next one.
Next up: The final boss of TH01 decompilation, YuugenMagan… if the current
or newly incoming TH01 funds happen to be enough to cover the entire fight.
If they don't turn out to be, I will have to pass the time with some Seihou
work instead, missing the TH01 anniversary deadline as a result.Edit (2022-07-18): Thanks to Yanga for
securing the funding for YuugenMagan after all! That fight will feature
slightly more than half of all remaining code in TH01's
REIIDEN.EXE and the single biggest function in all of PC-98
Touhou, let's go!
More than 50% of all PC-98 Touhou game code has now been
reverse-engineered! 🎉 While this number isn't equally distributed among the
games, we've got one game very close to 100% and reverse-engineered most of
the core features of two others. During the last 32 months of continuous
funding, I've averaged an overall speed of 1.11% total RE per month. That
looks like a decent prediction of how much more time it will take for 100%
across all games – unless, of course, I'd get to work towards some of the
non-RE goals in the meantime.
70 functions left in TH01, with less than 10,000 ASM instructions
remaining! Due to immense hype, I've temporarily raised the cap by 50% until
August 15. With the last TH01 pushes delivering at roughly 1.5× of the
currently calculated average speed, that should be more than enough to get
TH01 done – especially since I expect YuugenMagan to come with lots of
redundant code. Therefore, please also request a secondary priority for
these final TH01 RE contributions.
So, how did this card-flipping stage obstacle delivery get so horribly
delayed? With all the different layouts showcased in the 28 card-flipping
stages, you'd expect this to be among the more stable and bug-free parts of
the codebase. Heck, with all stage objects being placed on a 32×32-pixel
grid, this is the first TH01-related blog post this year that doesn't have
to describe an alignment-related unblitting glitch!
That alone doesn't mean that this code is free from quirky behavior though,
and we have to look no further than the first few lines of the collision
handling for round bumpers to already find a whole lot of that. Simplified,
they do the following:
Immediately, you wonder why these assignments only exist for the Y
coordinate. Sure, hitting a bumper from the left or right side should happen
less often, but it's definitely possible. Is it really a good idea to warp
the Orb to the top or bottom edge of a bumper regardless?
What's more important though: The fact that these immediate assignments
exist at all. The game's regular Orb physics work by producing a Y velocity
from the single force acting on the Orb and a gravity factor, and are
completely independent of its current Y position. A bumper collision does
also apply a new force onto the Orb further down in the code, but these
assignments still bypass the physics system and are bound to have
some knock-on effect on the Orb's movement.
To observe that effect, we just have to enter Stage 18 on the 地獄/Jigoku route, where it's particularly trivial to
reproduce. At a 📝 horizontal velocity of ±4,
these assignments are exactly what can cause the Orb to endlessly
bounce between two bumpers. As rudimentary as the Orb's physics may be, just
letting them do their work would have entirely prevented these loops:
One of at least three infinite bumper loop constellations within just
this 10×5-tile section of TH01's Stage 18 on the 地獄/Jigoku route. With an effective 56 horizontal
pixels between both hitboxes, the Orb would have to travel an absolute
Y distance of at least 16 vertical pixels within
(56 / 4) = 14 frames to escape the
other bumper's hitbox. If the initial bounce reduces the Orb's Y
velocity far enough for it to not manage that distance the first time,
it will never reach the necessary speed again. In this loop, the
bounce-off force even stabilizes, though this doesn't have to happen.
The blue areas indicate the pixel-perfect* hitboxes of each bumper.
TH01 bumper collision handling without ZUN's manual assignment of the Y
coordinate. The Orb still bounces back and forth between two bumpers
for a while, but its top position always follows naturally
from its Y velocity and the force applied to it, and gravity wins out
in the end. The blue areas indicate the pixel-perfect* hitboxes of each bumper.
Now, you might be thinking that these Y assignments were just an attempt to
prevent the Orb from colliding with the same bumper again on the next frame.
After all, those 24 pixels exactly correspond to ⅓ of the height of a
bumper's hitbox with an additional pixel added on top. However, the game
already perfectly prevents repeated collisions by turning off collision
testing with the same bumper for the next 7 frames after a collision. Thus,
we can conclude that ZUN either explicitly coded bumper collision handling
to facilitate these loops, or just didn't take out that code after
inevitably discovering what it did. This is not janky code, it's not a
glitch, it's not sarcasm from my end, and it's not the game's physics being
bad.
But wait. Couldn't these assignments just be a remnant from a time in
development before ZUN decided on the 7-frame delay on further
collisions? Well, even that explanation stops holding water after the next
few lines of code. Simplified, again:
What's important here is the part that's not in the code – namely,
anything that handles X velocities of -8 or +8. In those cases, the Orb
simply continues in the same horizontal direction. The manual Y assignment
is the only part of the code that actually prevents a collision there, as
the newly applied force is not guaranteed to be enough:
An infinite loop across three bumpers, made possible by the edge of the
playfield and bumper bars on opposite sides, an unchanged horizontal
direction, and the Y assignments neatly placing the Orb on either the
top or bottom side of a bumper. The alternating sign of the force
further ensures that the Orb will travel upwards half the time,
canceling out gravity during the short time between two hitboxes.
With the unchanged horizontal direction and the Y assignments removed,
nothing keeps an Orb at ±8 pixels per frame from flying into/over a
bumper. The collision force pushes the Orb slightly, but not enough to
truly matter. The final force sends the Orb on a significant downward
trajectory beyond the next bumper's hitbox, breaking the original loop.
Forgetting to handle ⅖ of your discrete X velocity cases is simply not
something you do by accident. So we might as well say that ZUN deliberately
designed the game to behave exactly as it does in this regard.
Bumpers also come in vertical or horizontal bar shapes. Their collision
handling also turns off further collision testing for the next 7 frames, and
doesn't do any manual coordinate assignment. That's definitely a step up in
cleanliness from round bumpers, but it doesn't seem to keep in mind that the
player can fire a new shot every 4 frames when standing still. That makes it
immediately obvious why this works:
The green numbers show the amount of
frames since the last detected collision with the respective bumper bar,
and indicate that collision testing with the bar below is currently
disabled.
That's the most well-known case of reducing the Orb's horizontal velocity to
0 by exactly hitting it with shots in its center and then button-mashing it
through a horizontal bar. This also works with vertical bars and yields even
more interesting results there, but if we want to have any chance of
understanding what happens there, we have to first go over some basics:
Collision detection for all stage obstacles is done in row-major
order from the top-left to the bottom-right corner of the
playfield.
All obstacles are collision-tested independently from each other, with
the collision response code immediately following the test.
The hitboxes for bumper bars extend far past their 32×32 sprites to make
sure that the Orb can collide with them from any side. They are a
pixel-perfect* 87×56 pixels for horizontal bars, and 57×87 pixels for
vertical ones. Yes, that's no typo, they really do differ in one pixel.
Changing the Y velocity during such a collision just involves applying a
new force with the magnitude of the negated current Y velocity, which can be
done multiple times during a frame without changing the result. This
explains why the force is correctly inverted in the clip above, despite the
Orb colliding with two bumpers simultaneously.
Lacking a similar force system, the X coordinate is simply directly
inverted.
However, if that were everything the game did, kicking the Orb into a column
of vertical bumper bars would lead them to behave more like a rope that the
Orb can climb, as the initial collision with two hitboxes cancels out the
intended sign change that reflects the Orb away from the bars:
This footage was recorded without the workaround I am about to describe.
It does not reflect the behavior of the original game. You
cannot do this in the original game.
While the visualization reveals small sections where three hitboxes
overlap, the Orb can never actually collide with three of them at the
same time, as those 3-hitbox regions are 2 pixels smaller than they
would need to be to fit the Orb. That's exactly the difference between
using < rather than <= in these hitbox
comparisons.
While that would have been a fun gameplay mechanic on its own, it
immediately breaks apart once you place two vertical bumper bars next to
each other. Due to how these bumper bar hitboxes extend past their sprites,
any two adjacent vertical bars will end up with the exact same hitbox in
absolute screen coordinates. Stage 17 on the
魔界/Makai route contains exactly such a layout:
The collision handlers of adjacent vertical bars always activate in the
same frame, independently invert the Orb's X velocity, and therefore
fully cancel out their intended effect on the Orb… if the game did not
have the workaround I am about to describe. This cannot happen
in the original game.
ZUN's workaround: Setting a "vertical bumper bar block flag" after any
collision with such a bar, which simply disables any collision with
any vertical bar for the next 7 frames. This quick hack made all
vertical bars work as intended, and avoided the need for involving the Orb's
X velocity in any kind of physics system.
Edit (2022-07-12): This flag only works around glitches
that would be caused by simultaneously colliding with more than one vertical
bar. The actual response to a bumper bar collision still remains unaffected,
and is very naive:
Horizontal bars always invert the Orb's Y velocity
Vertical bars invert either the Y or X velocity depending on whether
the Orb's current X velocity is 0 (Y) or not (X)
These conditions are only correct if the Orb comes in at an angle roughly
between 45° and 135° on either side of a bar. If it's anywhere close to 0°
or 180°, this response will be incorrect, and send the Orb straight
through the bar. Since the large hitboxes make this easily possible, you can
still get the Orb to climb a vertical column, or glide along a horizontal
row:
Here's the hitbox overlay for
地獄/Jigoku Stage 19, and here's an updated
version of the 📝 Orb physics debug mod that
now also shows bumper bar collision frame numbers:
2022-07-10-TH01OrbPhysicsDebug.zip
See the th01_orb_debug
branch for the code. To use it, simply replace REIIDEN.EXE, and
run the game in debug mode, via game d on the DOS prompt. If you
encounter a gameplay situation that doesn't seem to be covered by this blog
post, you can now verify it for yourself. Thanks to touhou-memories for bringing these
issues to my attention! That definitely was a glaring omission from the
initial version of this blog post.
With that clarified, we can now try mashing the Orb into these two vertical
bars:
At first, that workaround doesn't seem to make a difference here. As we
expect, the frame numbers now tell us that only one of the two bumper bars
in a row activates, but we couldn't have told otherwise as the number of
bars has no effect on newly applied Y velocity forces. On a closer look, the
Orb's rise to the top of the playfield is in fact caused by that
workaround though, combined with the unchanged top-to-bottom order of
collision testing. As soon as any bumper bar completed its 7
collision delay frames, it resets the aforementioned flag, which already
reactivates collision handling for any remaining vertical bumper bars during
the same frame. Look out for frames with both a 7 and a 1, like the one marked in the video above:
The 7 will always appear before
the 1 in the row-major order. Whenever
this happens, the current oscillation period is cut down from 7 to 6
frames – and because collision testing runs from top to bottom, this will
always happen during the falling part. Depending on the Y velocity, the
rising part may also be cut down to 6 frames from time to time, but that one
at least has a chance to last for the full 7 frames. This difference
adds those crucial extra frames of upward movement, which add up to send the
Orb to the top. Without the flag, you'd always see the Orb oscillating
between a fixed range of the bar column.
Finally, it's the "top of playfield" force that gradually slows down the Orb
and makes sure it ultimately only moves at sub-pixel velocities, which have
no visible effect. Because
📝 the regular effect of gravity is reset with
each newly applied force, it's completely negated during most of the climb.
This even holds true once the Orb reached the top: Since the Orb requires a
negative force to repeatedly arrive up there and be bounced back, this force
will stay active for the first 5 of the 7 collision frames and not move the
Orb at all. Once gravity kicks in at the 5th frame and adds 1 to
the Y velocity, it's already too late: The new velocity can't be larger than
0.5, and the Orb only has 1 or 2 frames before the flag reset causes it to
be bounced back up to the top again.
Portals, on the other hand, turn out to be much simpler than the old
description that ended up on Touhou Wiki in October 2005 might suggest.
Everything about their teleportations is random: The destination portal, the
exit force (as an integer between -9 and +9), as well as the exit X
velocity, with each of the
📝 5 distinct horizontal velocities having an
equal chance of being chosen. Of course, if the destination portal is next
to the left or right edge of the playfield and it chooses to fire the Orb
towards that edge, it immediately bounces off into the opposite direction,
whereas the 0 velocity is always selected with a constant 20% probability.
The selection process for the destination portal involves a bit more than a
single rand() call. The game bundles all obstacles in a single
structure of dynamically allocated arrays, and only knows how many obstacles
there are in total, not per type. Now, that alone wouldn't have much
of an impact on random portal selection, as you could simply roll a random
obstacle ID and try again if it's not a portal. But just to be extra cute,
ZUN instead iterates over all obstacles, selects any non-entered portal with
a chance of ¼, and just gives up if that dice roll wasn't successful after
16 loops over the whole array, defaulting to the entered portal in that
case.
In all its silliness though, this works perfectly fine, and results in a
chance of 0.7516(𝑛 - 1) for the Orb exiting out of the
same portal it entered, with 𝑛 being the total number of portals in a
stage. That's 1% for two portals, and 0.01% for three. Pretty decent for a
random result you don't want to happen, but that hurts nobody if it does.
The one tiny ZUN bug with portals is technically not even part of the newly
decompiled code here. If Reimu gets hit while the Orb is being sent through
a portal, the Orb is immediately kicked out of the portal it entered, no
matter whether it already shows up inside the sprite of the destination
portal. Neither of the two portal sprites is reset when this happens,
leading to "two Orbs" being visible simultaneously.
This makes very little sense no matter how you look at it. The Orb doesn't
receive a new velocity or force when this happens, so it will simply
re-enter the same portal once the gameplay resumes on Reimu's next life:
That left another ½ of a push over at the end. Way too much time to finish
FUUIN.exe, way too little time to start with Mima… but the bomb
animation fit perfectly in there. No secrets or bugs there, just a bunch of
sprite animation code wasting at least another 82 bytes in the data segment.
The special effect after the kuji-in sprites uses the same single-bitplane
32×32 square inversion effect seen at the end of Kikuri's and Sariel's
entrance animation, except that it's a 3-stack of 16-rings moving at 6, 7,
and 8 pixels per frame respectively. At these comparatively slow speeds, the
byte alignment of each square adds some further noise to the discoloration
pattern… if you even notice it below all the shaking and seizure-inducing
hardware palette manipulation.
And yes, due to the very destructive nature of the effect, the game does in
fact rely on it only being applied to VRAM page 0. While that will cause
every moving sprite to tear holes into the inverted squares along its
trajectory, keeping a clean playfield on VRAM page 1 is what allows all that
pixel damage to be easily undone at the end of this 89-frame animation.
Next up: Mima! Let's hope that stage obstacles already were the most complex
part remaining in TH01…
The "bad" news first: Expanding to Stripe in order to support Google Pay
requires bureaucratic effort that is not quite justified yet, and would only
be worth it after the next price increase.
Visualizing technical debt has definitely been overdue for a while though.
With 1 of these 2 pushes being focused on this topic, it makes sense to
summarize once again what "technical debt"
means in the context of ReC98, as this info was previously kind of scattered
over multiple blog posts. Mainly, it encompasses
any ZUN-written code
that we did name and reverse-engineer,
but which we simply moved out into dedicated files that are then
#included back into the big .ASM translation units,
without worrying about decompilation or proving undecompilability for
now.
Technically (ha), it would also include all of master.lib, which has
always been compiled into the binaries in this way, and which will require
quite a bit of dedicated effort to be moved out into a properly linkable
library, once it's feasible. But this code has never been part of any
progress metric – in fact, 0% RE is
defined as the total number of x86 instructions in the binary minus
any library code. There is also no relation between instruction numbers and
the time it will take to finalize master.lib code, let alone a precedent of
how much it would cost.
If we now want to express technical debt as a percentage, it's clear where
the 100% point would be: when all RE'd code is also compiled in from a
translation unit outside the big .ASM one. But where would 0% be? Logically,
it would be the point where no reverse-engineered code has ever been moved
out of the big translation units yet, and nothing has ever been decompiled.
With these boundary points, this is what we get:
Not too bad! So it's 6.22% of total RE that we will have to revisit at some
point, concentrated mostly around TH04 and TH05 where it resulted from a
focus on position independence. The prices also give an accurate impression
of how much more work would be required there.
But is that really the best visualization? After all, it requires an
understanding of our definition of technical debt, so it's maybe not the
most useful measurement to have on a front page. But how about subtracting
those 6.22% from the number shown on the RE% bars? Then, we get this:
Which is where we get to the good news: Twitter surprisingly helped me out
in choosing one visualization over the other, voting
7:2 in favor of the Finalized version. While this one requires
you to manually calculate € finalized - € RE'd to
obtain the raw financial cost of technical debt, it clearly shows, for the
first time, how far away we are from the main goal of fully decompiling all
5 games… at least to the extent it's possible.
Now that the parser is looking at these recursively included .ASM files for
the first time, it needed a small number of improvements to correctly handle
the more advanced directives used there, which no automatic disassembler
would ever emit. Turns out I've been counting some directives as
instructions that never should have been, which is where the additional
0.02% total RE came from.
One more overcounting issue remains though. Some of the RE'd assembly slices
included by multiple games contain different if branches for
each game, like this:
; An example assembly file included by both TH04's and TH05's MAIN.EXE:
if (GAME eq 5)
; (Code for TH05)
else
; (Code for TH04)
endif
Currently, the parser simply ignores if, else, and
endif, leading to the combined code of all branches being
counted for every game that includes such a file. This also affects the
calculated speed, and is the reason why finalization seems to be slightly
faster than reverse-engineering, at currently 471 instructions per push
compared to 463. However, it's not that bad of a signal to send: Most of the
not yet finalized code is shared between TH04 and TH05, so finalizing it
will roughly be twice as fast as regular reverse-engineering to begin with.
(Unless the code then turns out to be twice as complex than average code…
).
For completeness, finalization is now also shown as part of the per-commit metrics. Now it's clearly visible what I was
doing in those very slow five months between P0131 and P0140, where
the progress bar didn't move at all: Repaying 3.49% of previously
accumulated technical debt across all games. 👌
As announced, I've also implemented a new caching system for this website,
as the second main feature of these two pushes. By appending a hash string
to the URLs of static resources, your browser should now both cache them
forever and re-download them once they did change on the server. This
avoids the unnecessary (and quite frankly, embarrassing) re-requests for all
static resources that typically just return a 304 Not Modified
response. As a result, the blog should now load a bit faster on repeated
visits, especially on slower connections. That should allow me to
deliberately not paginate it for another few years, without it getting all
too slow – and should prepare us for the day when our first game
reaches 100% and the server will get smashed.
However, I am open to changing the progress blog link in the
navigation bar at the top to the list of tags, once
people start complaining.
Apart frome some more invisible correctness and QoL improvements, I've also
prepared some new funding goals, but I'll cover those once the store
reopens, next year. Syntax highlighting for code snippets would have also
been cool, but unfortunately didn't make it into those two pushes. It's
still on the list though!
Next up: Back to RE with the TH03 score file format, and other code that
surrounds it.
📝 Posted:
🏷 Tags:
Made it through almost three years without a price increase! It's been
overdue for a while, though.
With the last months being full of rather research- and documentation-heavy
pushes, I've been just about able to keep up with the existing
subscriptions. By now, the amount of quality control and documentation I
found myself putting into this project has far surpassed the raw
reverse-engineering work. Back at the beginning of 2019 when I decided on
the previous push price of 30 €, I didn't have this blog nor the current
aspirations at code quality. Neither of these have ever been reflected in
the price, and I still find it hard to put a number on them. On the other
hand, I continue to dislike the typical Patreon model of no inherent defined
obligations on my part, and no direct association of the resulting work with
the person who funded it. You might have noticed that I don't use the word
"donations" anywhere, and instead refer to them as "orders" or "purchases" –
and that's precisely for this reason.
The result, however, has been a sold-out store for pretty much all of 2021.
I can only begin to imagine how much potential revenue I've already lost
from people who might have wanted to contribute at one point, but couldn't,
and have already written off this project…
Raising prices is pretty much the only way to get the pending workload back
to a more comfortable amount. I also thought about a two-tiered system: Have
a documentation-less option for 30 €, and take 60 € for any push that should
be accompanied by a blog post. However, skimping on documentation will
compromise the quality of the code as well. Writing these blog posts
presents another chance of improving it before release, which has made quite
a difference on many occasions. And after all, this documentation is the one
thing about ReC98 that people mainly interact with. As long as we haven't
hit 100% RE, the actual code seems to be an afterthought, which is perfectly
understandable: Why start work on a bigger mod or port now if the code is
steadily improving in every aspect, and it all will be just a bit more
maintainable in a few months?
But why go more commercial then, and especially now? If the recent attention
to spaztron64's PC-98 Touhou
collection package is any indication, ReC98 has a way bigger career
potential than the dead-end RL job I found myself in. Demand for fixed
translations and replay
support is definitely there – and given that these haven't been done so
far, it's very likely that I'll end up as the one to implement such mods,
especially if that should happen before reaching 100% RE or PI. People also
still seem to want* a port to IBM-compatible DOS,
📝 even though this makes no sense? But if
this is something you all want to pay for, then sure, why not.
And even right now, working on ReC98 sure beats writing junk software using
ill-suited technologies for highly corporate clients, or living close to a
world where academic papers are valued higher than working and maintained
code. I am in fact very happy whenever I'm done with that for the day, and
get to work on ReC98! Who would have thought.
So let's try to grow this into an actual business and raise prices to match
demand, going up to a nicely divisible 60 € per push. If you all still
manage to regularly sell out the store at this level and I get to
raise prices again, I should be able to reduce RL work further and therefore
raise the cap as well. Now that I've also clarified a potential route
towards self-employment, I'm going to react to these sell-out events more
quickly, and with smaller raises. So, no further immediate doubling in the
future.
Now, will this delay the currently highly awaited 100% completion of TH01
past August 2022, the 25th anniversary of its release? We'll see once we're
back to an almost empty backlog, after I'm done with the TH01 Sariel fight.
I'm hopeful that such a price increase will give a new voice to the goals
and priorities of less wealthy potential patrons. This crowdfunding is very
much designed to be hacked by "microtransactions" – small contributions with
specific requests that require other, larger generic contributions to be
fulfilled – and I'd like to see more of that. 😛 And even if 60 € per push
is already more than the combined fandom wants to pay, that means I can get
the 📝 16-bit build system done before the
first big 100% release. (Trust me, you really want that!)
I will still deliver the entire current backlog at the value the
contributions were originally purchased at. Due to the way the cap has to be
calculated, these contributions now appear to have doubled in value. All
existing subscriptions will then pay for half of their original pushes
starting with their respective December 2021 transaction.
Next up: A bunch of smaller website features, including:
a caching strategy for static content,
a third set of percentage bars to visualize the remaining technical
debt,
and, hopefully, some new payment methods that expand the number of
countries I can accept money from. (Yes, this was requested at one point
earlier this year!)
Secured a 22.5-hour RL workweek to leave plenty of time for this project,
Touhou Patch Center's commissioned MediaWiki update work is also nearing
completion, time to reopen the store! Since it's been a long time, here's
an overview of where we currently are in each game and binary, and what
the next logical step would be:
TH02:
MAIN.EXE: The final PC-98-specific low-level rendering functions are blocked by a single inconsistent and thus undecompilable assembly instruction. Rather than going for 📝 code generation and turning the rest of the function into a mess, I'd like to introduce a new build step between compilation and linking to patch "mistakes" like these. This would be an investment of 1-2 pushes into more readable code. Otherwise, I could continue with
player character movement,
player shots and the control code for the three shot types, or
bomb rendering.
MAINE.EXE:main() and the congratulation picture screens.
OP.EXE: Finalizing the ZUN Soft logo animation, decompiling the game title slide-in animation, decompiling the High Score menu in parallel with TH05, and then we're done!
MAIN.EXE:
There's a lot of partially reverse-engineered but not yet decompiled code, including all of this game's custom entity types. Covering that would significantly boost finalization% for very little money. Otherwise, we could go for either
Gengetsu's boss script
HUD rendering (in parallel with TH05)
player update code (in parallel with TH05), required for all midbosses in this game
player shot control functions
the end-of-stage bonus calculation
MAINE.EXE: High score name entry.
TH05:
OP.EXE: Finalizing the ZUN Soft logo animation, decompiling the High Score menu in parallel with TH04, and then we're done!
MAIN.EXE: Got quite a lot of segment splits where we could immediately continue:
midboss and boss script code, either continuing with the in-game order and the Stage 2 midboss fight, or going directly for
Mai & Yuki,
the Extra Stage midboss,
or EX-Alice
stage tile rendering
player update code (in parallel with TH04)
items and extends
bomb rendering
the single-color areas of boss backgrounds, which use the GRCG's TDW mode
HUD rendering (in parallel with TH05)
boss sprite rendering boilerplate
player shot collision detection and rendering
MAINE.EXE: The staff roll animation.
But as always, you can request pretty much any other part of any game.
We're now at a pretty good place as far as arbitrary requests are
concerned, as I simply can't decide myself where to put all the current
pending contributions in the funding backlog. 😅 By
spending only the missing amount of money to complete any of those, you can
capture any of those "fractional" contributions towards a specific goal.
The next specific requests are going to set the priorities of this project
for quite some time! The best strategy: Spend a low amount of money on
something very specific, and watch as existing generic contributions will
necessarily have to be put towards making that specific goal happen 😛
Whoops, the build was broken again? Since
P0127 from
mid-November 2020, on TASM32 version 5.3, which also happens to be the
one in the DevKit… That version changed the alignment for the default
segments of certain memory models when requesting .386
support. And since redefining segment alignment apparently is highly
illegal and absolutely has to be a build error, some of the stand-alone
.ASM translation units didn't assemble anymore on this version. I've only
spotted this on my own because I casually compiled ReC98 somewhere else –
on my development system, I happened to have TASM32 version 5.0 in the
PATH during all this time.
At least this was a good occasion to
get rid of some
weird segment alignment workarounds from 2015, and replace them with the
superior convention of using the USE16 modifier for the
.MODEL directive.
ReC98 would highly benefit from a build server – both in order to
immediately spot issues like this one, and as a service for modders.
Even more so than the usual open-source project of its size, I would say.
But that might be exactly
because it doesn't seem like something you can trivially outsource
to one of the big CI providers for open-source projects, and quickly set
it up with a few lines of YAML.
That might still work in the beginning, and we might get by with a regular
64-bit Windows 10 and DOSBox running the exact build tools from the DevKit.
Ideally, though, such a server should really run the optimal configuration
of a 32-bit Windows 10, allowing both the 32-bit and the 16-bit build step
to run natively, which already is something that no popular CI service out
there offers. Then, we'd optimally expand to Linux, every other Windows
version down to 95, emulated PC-98 systems, other TASM versions… yeah, it'd
be a lot. An experimental project all on its own, with additional hosting
costs and probably diminishing returns, the more it expands…
I've added it as a category to the order form, let's see how much interest
there is once the store reopens (which will be at the beginning of May, at
the latest). That aside, it would 📝 also be
a great project for outside contributors!
So, technical debt, part 8… and right away, we're faced with TH03's
low-level input function, which
📝 once📝 again📝 insists on being word-aligned in a way we
can't fake without duplicating translation units.
Being undecompilable isn't exactly the best property for a function that
has been interesting to modders in the past: In 2018,
spaztron64 created an
ASM-level mod that hardcoded more ergonomic key bindings for human-vs-human
multiplayer mode: 2021-04-04-TH03-WASD-2player.zip
However, this remapping attempt remained quite limited, since we hadn't
(and still haven't) reached full position independence for TH03 yet.
There's quite some potential for size optimizations in this function, which
would allow more BIOS key groups to already be used right now, but it's not
all that obvious to modders who aren't intimately familiar with x86 ASM.
Therefore, I really wouldn't want to keep such a long and important
function in ASM if we don't absolutely have to…
… and apparently, that's all the motivation I needed? So I took the risk,
and spent the first half of this push on reverse-engineering
TCC.EXE, to hopefully find a way to get word-aligned code
segments out of Turbo C++ after all.
And there is! The -WX option, used for creating
DPMI
applications, messes up all sorts of code generation aspects in weird
ways, but does in fact mark the code segment as word-aligned. We can
consider ourselves quite lucky that we get to use Turbo C++ 4.0, because
this feature isn't available in any previous version of Borland's C++
compilers.
That allowed us to restore all the decompilations I previously threw away…
well, two of the three, that lookup table generator was too much of a mess
in C. But what an abuse this is. The
subtly different code generation has basically required one creative
workaround per usage of -WX. For example, enabling that option
causes the regular PUSH BP and POP BP prolog and
epilog instructions to be wrapped with INC BP and
DEC BP, for some reason:
a_function_compiled_with_wx proc
inc bp ; ???
push bp
mov bp, sp
; [… function code …]
pop bp
dec bp ; ???
ret
a_function_compiled_with_wx endp
Luckily again, all the functions that currently require -WX
don't set up a stack frame and don't take any parameters.
While this hasn't directly been an issue so far, it's been pretty
close: snd_se_reset(void) is one of the functions that require
word alignment. Previously, it shared a translation unit with the
immediately following snd_se_play(int new_se), which does take
a parameter, and therefore would have had its prolog and epilog code messed
up by -WX.
Since the latter function has a consistent (and thus, fakeable) alignment,
I simply split that code segment into two, with a new -WX
translation unit for just snd_se_reset(void). Problem solved –
after all, two C++ translation units are still better than one ASM
translation unit. Especially with all the
previous #include improvements.
The rest was more of the usual, getting us 74% done with repaying the
technical debt in the SHARED segment. A lot of the remaining
26% is TH04 needing to catch up with TH03 and TH05, which takes
comparatively little time. With some good luck, we might get this
done within the next push… that is, if we aren't confronted with all too
many more disgusting decompilations, like the two functions that ended this
push.
If we are, we might be needing 10 pushes to complete this after all, but
that piece of research was definitely worth the delay. Next up: One more of
these.
Alright, back to continuing the master.hpp transition started
in P0124, and repaying technical debt. The last blog post already
announced some ridiculous decompilations… and in fact, not a single
one of the functions in these two pushes was decompilable into
idiomatic C/C++ code.
As usual, that didn't keep me from trying though. The TH04 and TH05
version of the infamous 16-pixel-aligned, EGC-accelerated rectangle
blitting function from page 1 to page 0 was fairly average as far as
unreasonable decompilations are concerned.
The big blocker in TH03's MAIN.EXE, however, turned out to be
the .MRS functions, used to render the gauge attack portraits and bomb
backgrounds. The blitting code there uses the additional FS and GS segment
registers provided by the Intel 386… which
are not supported by Turbo C++'s inline assembler, and
can't be turned into pointers, due to a compiler bug in Turbo C++ that
generates wrong segment prefix opcodes for the _FS and
_GS pseudo-registers.
Apparently I'm the first one to even try doing that with this compiler? I
haven't found any other mention of this bug…
Compiling via assembly (#pragma inline) would work around
this bug and generate the correct instructions. But that would incur yet
another dependency on a 16-bit TASM, for something honestly quite
insignificant.
What we can always do, however, is using __emit__() to simply
output x86 opcodes anywhere in a function. Unlike spelled-out inline
assembly, that can even be used in helper functions that are supposed to
inline… which does in fact allow us to fully abstract away this compiler
bug. Regular if() comparisons with pseudo-registers
wouldn't inline, but "converting" them into C++ template function
specializations does. All that's left is some C preprocessor abuse
to turn the pseudo-registers into types, and then we do retain a
normal-looking poke() call in the blitting functions in the
end. 🤯
Yeah… the result is
batshitinsane.
I may have gone too far in a few places…
One might certainly argue that all these ridiculous decompilations
actually hurt the preservation angle of this project. "Clearly, ZUN
couldn't have possibly written such unreasonable C++ code.
So why pretend he did, and not just keep it all in its more natural ASM
form?" Well, there are several reasons:
Future port authors will merely have to translate all the
pseudo-registers and inline assembly to C++. For the former, this is
typically as easy as replacing them with newly declared local variables. No
need to bother with function prolog and epilog code, calling conventions, or
the build system.
No duplication of constants and structures in ASM land.
As a more expressive language, C++ can document the code much better.
Meticulous documentation seems to have become the main attraction of ReC98
these days – I've seen it appreciated quite a number of times, and the
continued financial support of all the backers speaks volumes. Mods, on the
other hand, are still a rather rare sight.
Having as few .ASM files in the source tree as possible looks better to
casual visitors who just look at GitHub's repo language breakdown. This way,
ReC98 will also turn from an "Assembly project" to its rightful state
of "C++ project" much sooner.
And finally, it's not like the ASM versions are
gone – they're still part of the Git history.
Unfortunately, these pushes also demonstrated a second disadvantage in
trying to decompile everything possible: Since Turbo C++ lacks TASM's
fine-grained ability to enforce code alignment on certain multiples of
bytes, it might actually be unfeasible to link in a C-compiled object file
at its intended original position in some of the .EXE files it's used in.
Which… you're only going to notice once you encounter such a case. Due to
the slightly jumbled order of functions in the
📝 second, shared code segment, that might
be long after you decompiled and successfully linked in the function
everywhere else.
And then you'll have to throw away that decompilation after all 😕 Oh
well. In this specific case (the lookup table generator for horizontally
flipping images), that decompilation was a mess anyway, and probably
helped nobody. I could have added a dummy .OBJ that does nothing but
enforce the needed 2-byte alignment before the function if I
really insisted on keeping the C version, but it really wasn't
worth it.
Now that I've also described yet another meta-issue, maybe there'll
really be nothing to say about the next technical debt pushes?
Next up though: Back to actual progress
again, with TH01. Which maybe even ends up pushing that game over the 50%
RE mark?
And indeed, I got to end my vacation with a lot of image format and
blitting code, covering the final two formats, .GRC and .BOS. .GRC was
nothing noteworthy – one function for loading, one function for
byte-aligned blitting, and one function for freeing memory. That's it –
not even a unblitting function for this one. .BOS, on the other hand…
…has no generic (read: single/sane) implementation, and is only
implemented as methods of some boss entity class. And then again for
Sariel's dress and wand animations, and then again for Reimu's
animations, both of which weren't even part of these 4 pushes. Looking
forward to decompiling essentially the same algorithms all over again… And
that's how TH01 became the largest and most bloated PC-98 Touhou game. So
yeah, still not done with image formats, even at 44% RE.
This means I also had to reverse-engineer that "boss entity" class… yeah,
what else to call something a boss can have multiple of, that may or may
not be part of a larger boss sprite, may or may not be animated, and that
may or may not have an orb hitbox?
All bosses except for Kikuri share the same 5 global instances of this
class. Since renaming all these variables in ASM land is tedious anyway, I
went the extra mile and directly defined separate, meaningful names for
the entities of all bosses. These also now document the natural order in
which the bosses will ultimately be decompiled. So, unless a backer
requests anything else, this order will be:
Konngara
Sariel
Elis
Kikuri
SinGyoku
(code for regular card-flipping stages)
Mima
YuugenMagan
As everyone kind of expects from TH01 by now, this class reveals yet
another… um, unique and quirky piece of code architecture. In
addition to the position and hitbox members you'd expect from a class like
this, the game also stores the .BOS metadata – width, height, animation
frame count, and 📝 bitplane pointer slot
number – inside the same class. But if each of those still corresponds to
one individual on-screen sprite, how can YuugenMagan have 5 eye sprites,
or Kikuri have more than one soul and tear sprite? By duplicating that
metadata, of course! And copying it from one entity to another
At this point, I feel like I even have to congratulate the game for not
actually loading YuugenMagan's eye sprites 5 times. But then again, 53,760
bytes of waste would have definitely been noticeable in the DOS days.
Makes much more sense to waste that amount of space on an unused C++
exception handler, and a bunch of redundant, unoptimized blitting
functions
(Thinking about it, YuugenMagan fits this entire system perfectly. And
together with its position in the game's code – last to be decompiled
means first on the linker command line – we might speculate that
YuugenMagan was the first boss to be programmed for TH01?)
So if a boss wants to use sprites with different sizes, there's no way
around using another entity. And that's why Girl-Elis and Bat-Elis are two
distinct entities internally, and have to manually sync their position.
Except that there's also a third one for Attacking-Girl-Elis,
because Girl-Elis has 9 frames of animation in total, and the global .BOS
bitplane pointers are divided into 4 slots of only 8 images each.
Same for SinGyoku, who is split into a sphere entity, a
person entity, and a… white flash entity for all three forms,
all at the same resolution. Or Konngara's facial expressions, which also
require two entities just for themselves.
And once you decompile all this code, you notice just how much of it the
game didn't even use. 13 of the 50 bytes of the boss entity class are
outright unused, and 10 bytes are used for a movement clamping and lock
system that would have been nice if ZUN also used it outside of
Kikuri's soul sprites. Instead, all other bosses ignore this system
completely, and just
party on
the X/Y coordinates of the boss entities directly.
As for the rendering functions, 5 out of 10 are unused. And while those
definitely make up less than half of the code, I still must have
spent at least 1 of those 4 pushes on effectively unused functionality.
Only one of these functions lends itself to some speculation. For Elis'
entrance animation, the class provides functions for wavy blitting and
unblitting, which use a separate X coordinate for every line of the
sprite. But there's also an unused and sort of broken one for unblitting
two overlapping wavy sprites, located at the same Y coordinate. This might
indicate that Elis could originally split herself into two sprites,
similar to TH04 Stage 6 Yuuka? Or it might just have been some other kind
of animation effect, who knows.
After over 3 months of TH01 progress though, it's finally time to look at
other games, to cover the rest of the crowdfunding backlog. Next up: Going
back to TH05, and getting rid of those last PI false positives. And since
I can potentially spend the next 7 weeks on almost full-time ReC98 work,
I've also re-opened the store until October!
📝 Posted:
🏷 Tags:
TH01 pellets are coming up next, and for the first time, we'll have the
chance to move hardcoded sprite data from ASM land to C land. As it would
turn out, bad luck with the 2-byte alignment at the end of
REIIDEN.EXE's data segment pretty much forces us to declare
TH01's pellet sprites in C if we want to decompile the final few pellet
functions without ugly workarounds for the float literals there. And while
I could have just converted them into a C array and called it a day, it
did raise the question of when we are going to do this The Right And
Moddable Way, by auto-converting actual image files into ASM or C arrays
during the build process. These arrays are even more annoying to edit in
C, after all – unlike TASM, the old C++ we have to work with doesn't
support binary number literals, only hexadecimal or, gasp, octal.
Without the explicit funding for such a converter,
I reached out to
GitHub, asking backers and outside contributors whether they'd be in
favor of it. As something that requires no RE skills and collides with
nothing else, it would be a perfect task for C/C++ coders who want to
support ReC98 with something other than money.
And surprisingly, those still exist!
Jonathan Campbell, of
DOSBox-X fame,
went ahead and implemented all the required functionality, within just a
few days. Thanks again! The result is probably a lot more portable than it
would have been if I had written it. Which is pretty relevant for future
port authors – any additional tooling we write ourselves should not
add to the list of problems they'll have to worry about.
Right now, all of the sprites are #included from the big ASM
dump files, which means that they have to be converted before those files
are assembled during the 32-bit build part. We could have introduced a
third distinct build step there, perhaps even a 16-bit one so that we can
use Turbo C++ 4.0J to also compile the converter… However, the more
reasonable option was to do this at the beginning of the 32-bit build
step, and add a 32-bit Windows C++ compiler to the list of tools required
for ReC98's build process.
And the best choice for ReC98 is, in fact… 🥁… the 20-year-old Borland C++
5.5 freeware release.
See the README for a lengthy justification, as well as
download links.
So yes, all sprites mentioned in the GitHub issue can now be modded by
simply editing .BMP files, using an image editor of your choice. 🖌
And now that that's dealt with, it's finally time for more actual
progress! TH01 pellets coming tomorrow.
📝 Posted:
🏷 Tags:
Did WindowsTiger just cover
2% over all games on his
own? While not all of that passed my review, +1.59% RE and +1.66% PI
over all 5 games is still pretty noteworthy, and comfortably pushes TH05
over the 25% mark in RE, and the 60% mark in PI.
However.
While I definitely do appreciate such contributions, reviewing and
adapting these to my current code organization standards also takes more
time than I'd like it to take. And taken to this level, it does
kind of undermine this crowdfunding project, causing both a literal
denial of service and exactly the stress that this crowdfunding was
designed to avoid. Most of the time, I can't merge all of that as-is
without knowingly creating annoyances down the line. But I don't want to
just ignore it either, or reject every non-perfect commit…
That's also why I let it slide this time, due to some of the RE work in
there being genuinely amazing. In the future though, be aware that your
chance of having your work merged diminishes the further you move ahead of
my current master branch. In extreme cases like this one, I'll
then just be waiting until enough generic reverse-engineering pushes have
accrued, and treat the merge as regular work.
But now, time to continue with the regular programming… I am kind
of exhausted from all of this, so no bullets for the next two
Touhou Patch Center pushes, still… Good thing there's still plenty of
simpler things with big percentage gains to be done:
WindowsTiger mostly focused on OP.EXE which I tended to
neglect, as the big MAIN executables seemed to be more
interesting to my backers. (It's not like anyone ever requestedOP to be done either – like, who even cares about boring menu
source code, right?) Good that I therefore sort of left it as low-hanging
fruit to be grabbed by outside contributors – because now, TH04's and
TH05's OP.EXE are close to 100% position-independence. The
GENSOU.SCR format is pretty much the only thing missing there
right now, so let's finally go all the way there, I'd say.
And in TH05, there's still Reimu's shot type functions left to be
decompiled.
With no feedback to 📝 last week's blog post,
I assume you all are fine with how things are going? Alright then, another
one towards position independence, with the same approach as before…
Since -Tom- wanted to learn something about how the PC-98
EGC is used in TH04 and TH05, I took a look at master.lib's
egc_shift_*() functions. These simply do a hardware-accelerated
memmove() of any VRAM region, and are used for screen shaking
effects. Hover over the image below for the raw effect:
Then, I finally wanted to take a look at the bullet structures, but it
required way too much reverse-engineering to even start within ¾ of
a position independence push. Even with the help of uth05win –
bullet handling was changed quite a bit from TH04 to TH05.
What I ultimately settled on was more raw, "boring" PI work based around
an already known set of functions. For this one, I looked at vector
construction… and this time, that actually made the games a little
bit more position-independent, and wasn't just all about removing
false positives from the calculation. This was one of the few sets of
functions that would also apply to TH01, and it revealed just how
chaotically that game was coded. This one commit shows three ways how ZUN
stored regular 2D points in TH01:
"regularly", like in master.lib's Point structure (X
first, Y second)
reversed, (Y first and X second), then obviously with two distinct
variables declared next to each other
… yeah. But in more productive news, this did actually lay the
groundwork for TH04 and TH05 bullet structures. Which might even be coming
up within the next big, 5-push order from Touhou Patch Center? These are
the priorities I got from them, let's see how close I can get!
So, here we have the first two pushes with an explicit focus on position
independence… and they start out looking barely different from regular
reverse-engineering? They even already deduplicate a bunch of item-related
code, which was simple enough that it required little additional work?
Because the actual work, once again, was in comparing uth05win's
interpretations and naming choices with the original PC-98 code? So that
we only ended up removing a handful of memory references there?
(Oh well, you can mod item drops now!)
So, continuing to interpret PI as a mere by-product of reverse-engineering
might ultimately drive up the total PI cost quite a bit. But alright then,
let's systematically clear out some false positives by looking at
master.lib function calls instead… and suddenly we get the PI progress we
were looking for, nicely spread out over all games since TH02. That kinda
makes it sound like useless work, only done because it's dictated by some
counting algorithm on a website. But decompilation will want to convert
all of these values to decimal anyway. We're merely doing that right now,
across all games.
Then again, it doesn't actually make any game more
position-independent, and only proves how position-independent it already
was. So I'm really wondering right now whether I should just rush
actual position independence by simply identifying structures and
their sizes, and not bother with members or false positives until that's
done. That would certainly get the job done for TH04 and TH05 in just a
few more pushes, but then leave all the proving work (and the road
to 100% PI on the front page) to reverse-engineering.
I don't know. Would it be worth it to have a game that's "maybe
fully position-independent", only for there to maybe be rare edge
cases where it isn't?
Or maybe, continuing to strike a balance between identifying false
positives (fast) and reverse-engineering structures (slow) will continue
to work out like it did now, and make us end up close to the current
estimate, which was attractive enough to sell out the crowdfunding for the
first time… 🤔
Please give feedback! If possible, by Friday evening UTC+1, before I start
working on the next PI push, this time with a focus on TH04.
Then again… probably only while the remote player is not moving, because the chance for a human to replicate the AI's infamous erratic dodging is fairly low.
This surely must have been left in on purpose for us to laugh about it one day?
Shuusou Gyoku P0275
Touhou Patch Center on Open Collective
The 4 
Stage 4 Reimu's spinning orbs. Note how the game uses two different sets
of sprites just to have two different outline colors. This was probably
better than messing with the palette, which can easily cause unintended
effects if you only have 16 colors to work with. Heck, 
The chasing cross bullets, seen in Phase 14 of the same Stage 6 Yuuka
fight. Featuring some smart sprite work, making use of point symmetry to
achieve a fluid animation in just 4 frames. This is
TH01 Anniversary Edition, version P0239
TH03
TH04
TH05
, past right edge of current row
gaiji. Not to be confused with 
gaiji.
gaiji.
gaiji.
gaiji.
gaiji.
gaiji.
that Neko Project II auto-generates if you
don't provide either.
from the bottom of the playfield within very specifically calculated
random ranges… which are then rendered at byte-aligned VRAM positions, while
collision detection still uses their actual pixel position. Since I don't
want to sound like a broken record all too much, I'll just direct you to
