Emulator

According to flacs, everything is rendering off screen which is pretty weird. I'm guessing the game renders the entire backdrops to texture or something and then displays it behind the game and we're doing something wrong.

This issue seems to be related to various scrolling scenes, such as the loading screen. The game uses the scissor offset for this, but for some reason it adds 1024 to the value, which causes things to not show up correctly in Dolphin (though it works on console). This offset remains even after the scrolling is finished (so stuff ends up stuck at 1024, 0 or 0, 1024 when it should be at 0, 0). Note that in addition to gameplay and cutscenes being white screens, the title screen is a white screen if you return to it from the menu (though it renders correctly the first time). Forcing the scissor offset to be 171 (which functions as 0) lets you see the game, though it breaks the scrolling effects.

I've recorded several fifologs of different scrolling scenes, which should help cover different scenarios ingame (specifically, SceneLoading and StageUIRetry are covered, but StageUIGameOver hasn't been covered since it doesn't seem to be available in the tutorial and I don't want to play too much of the game). Note that these fifologs are large (~100 MB each when uncompressed) and long (~400-600 frames) - the main goal is to have something reproducible I can use for comparison purposes. The game runs at 30 FPS normally, though the fifologs might play back at a different rate.

Adding a game patch to change the 1024 value to 0 also makes the game render correctly (this value is a float at address 80361108; the hex value is 44800000) - as far as I can tell, there are no artefacts from this patch. However, it should be possible to emulate the 1024 offset correctly, so this is just a temporary workaround.

[OnFrame_Enabled]
$Disable 1024 scissor offset
[OnFrame]
$Disable 1024 scissor offset
0x80361108:dword:0x00000000

It's also important to make sure that any changes to this don't cause regressions for #8327 as Super Mario Galaxy uses scissor offsets for the boss roar effect.

Messy notes: https://gist.github.com/Pokechu22/5f83afb548bef8d75d3575d1c02bd518

https://dolphin-emu.org/download/dev/c0488de4829cb3a7d1d76522cee821ec8ad03f95/