TASEmulators / TASEmulators/BizHawk

[Neshawk] Graphical glitches at Uchuu Keibitai SDF's intro cutscene

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Core: NesHawk Inaccuracy
Dominant language
C#
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Description

If you wait a bit at Uchuu Keibitai SDF's title screen, a cutscene showing your ship's stats will appear. It uses a split screen effect, which isn't emulated correctly in Neshawk. This is how it looks like there:

https://user-images.githubusercontent.com/24638400/226118729-dae72bf1-0aa5-4f56-90ed-6609f040a814.mp4

FCEUX in old PPU mode emulates it correctly (new PPU is also wrong). This is how it's supposed to look like:

https://user-images.githubusercontent.com/24638400/226118770-2c3fa022-e897-42bb-afa2-250daf504794.mp4

That matches how things look on real hardware (I verified). Other emulators that also emulate it correctly are Nestopia UE and puNES. One thing worth mentioning is that surprisingly enough, it's also partially glitched in Mesen.

I'm guessing this is a result of bad MMC5 emulation, which is the mapper used by the game.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce Uchuu Keibitai SDF's intro cutscene in Neshawk and compare the split-screen output with the provided real-hardware and emulator videos. Start by tracing Neshawk's MMC5 and PPU emulation paths; done means the ship-stats cutscene renders like the reference, including the split-screen effect.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp
Domain
computer-graphics
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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