Gekka no Yasoukyoku (SotN) ULJM05287 Software rendering oddities

[RokkumanX]

Game or games this happens in

ULJM05287

What area of the game

This happens on screens with visible skies such as the Entrance, Olrox Quarters and the Castle Keep. Also the Fire Demon/Flame Demon only appears in the inverted Alchemy Laboratory.

What happens

The Entrance:

Olrox Quarters:

Castle Keep:

Fire Demon/Flame Demon:

What should happen

This is a screenshot of the inverted Entrance sky and it appears not to have the checkered pattern, at least not to the naked eye and that is somewhat of what I'm expecting the rest of the skies to look like:

Without playing the PSX version, this was the fastest source of how the death animation for the Fire Demon/Flame demon would look like:

https://www.youtube.com/watch?v=4MaqpJYTM-c&t=102s

GE frame capture

This is the GE Frame Dumps from the Castle Keep and Olrox Quarters where the checkered skies are present all time. GE Frame Dumps.zip

As Alucard mentioned in the screenshot above, the death animation of the Fire Demon/Flame Demon is so quick I'm not sure it's possible to get a Frame Dump.

Also, again the game is verified 100% here http://redump.org/disc/24765/

Platform

Windows

Mobile phone model or graphics card

NVIDIA GeForce GTX 1070

PPSSPP version affected

v1.14.4-1178

Last working version

Don't know unfortunately

Graphics backend (3D API)

OpenGL / GLES

Checklist

• [X] Test in the latest git build in case it's already fixed.
• [X] Search for other reports of the same issue.
• [X] Try resetting settings or older versions and include if the issue is related.
• [X] Try changing graphics settings to determine if one causes the glitch (especially speed hacks or enhancements/replacements.)
• [X] Include logs or screenshots of issue.

[unknownbrackets]

I'll look at these later, but the checkering could be dither and we'll just have to see how it lines up with a real PSP. Maybe there's something slightly off still about how the dither pattern is applied.

For the death animation, the way I've usually captured things like that is using the Windows GE debugger:

1. Debug -> GE debugger
2. About when you kill the enemy hit "Step Frame". It can be hard to catch, using alternate speed 25% could help. The goal is to catch before the death animation, you don't have to hit exactly on it.
3. Hit step frame until the glitch is about to be visible next frame. I usually use save states / rewind to try again if I miss this.
4. Hit "Record frame" when the next frame is going to show the glitch (whether or not the current one is.)

It's a bit of a pain but it's definitely possible. It's really about as hard as getting a screenshot of it.

-[Unknown]

[RokkumanX]

Thank you for the quick feedback!

I'll try what you suggested.

[unknownbrackets]

Hm, for the checkered pattern, here's the second frame dump's PSP image:

And software rendering:

There's some accuracy issues with the moon and a few other elements, but the dithering looks right. Vulkan and other hardware backends of course don't do any dithering, so they look different.

However, the screenshots you provided had "lines" in the checkering, which looks wrong. That's just because the display/screenshot has been resized to an unclean multiple of the PSP's resolution. So I don't think that's an issue.

The dithering is correct, and just (intentionally) missing in hardware rendering. The reason is that hardware rendering always forces things to 8888 (true color) as much as possible. Because of this, you typically don't get banding or other artifacts, but sometimes colors come out brighter or darker than they should have by a little bit. It's a pretty worthwhile tradeoff.

On the real PSP, graphics were often drawn using 5551, 565, or 4444 color depths. In a gradient, you can often clearly see banding in such a gradient. Since they didn't have the memory (and memory bandwidth) to use 8888, PSP games instead used an old technique called dithering. This intentionally does a checker matrix (exactly like you see in my above screenshots) to "interrupt" the banding. Although this doesn't look as good as true color, it looks better than not doing it.

Most games used dithering a bunch, actually.

-[Unknown]

[hrydgard]

Extremely minor technical correction to the above, though I'm guessing you just left it out for simplicity - dithering is not really old, it's a timeless technique thats actually still used in modern games with HDR rendering when converting to SDR display, can still get rid of banding in that situation! Usually larger blue noise textures are used these days instead of a small repeated matrix. Dithering is also used for audio bit depth reduction.

These days visual dithering is not as visible as the aggressive dither-to-16-bit color that was done on the PSP and Voodoo 2 for example though!

[unknownbrackets]

Heh, I did mean old as in timeless - but I didn't actually know dithering was used for audio as well (makes sense, of course.)

-[Unknown]

[RokkumanX]

Thank you both for your input in the matter.

Would playing on a 48" inch TV be the reason to why you can see the checkered pattern so clearly?

[unknownbrackets]

I mean, that would definitely make it look more visible, I'd think. But if you have it upscaling using a bilinear filter or some other screen scaling filter, it'd probably become less noticeable.

-[Unknown]

[hrydgard]

Try the new integer scaling option in Display layout & effects, just to make sure it's not some moire effect from scaling.

[LunaMoo]

C:SotN doesn't render 1:1 anyway since it's stretching PSOne res to match the PSP res, the game itself only allows to stretch or unstretch to/from widescreen, but it's always stretched unless a cheat like the one I made for EU version to render it with 1:1 native res is used.

Edit: I checked EU version same issue, althrough in different ways both PSP and PPSSPP get it wrong due to stretching that messes up the pattern in the PSP port of the game. With my 1:1 render resolution patch for this game the pattern looks right and doesn't create any visible lines, but I only ever made it for EU version.

[RokkumanX]

Thank you all for your input, for the last two days Alucard have been standing in the inverted /Black Marble Gallery killing endless and endless of Medusa heads leveling up to 99 and the Muramasa attack to 999.

He's up to 990 right now and tomorrow I can finally try out the new integer scaling everywhere in my hunt for a complete beastiary with all item drops.

The integer scaling looks really good but I haven't seen any skies with it yet.

I'll report back tomorrow.

[RokkumanX]

Well, it seems like the checkered pattern is still present with integer scaling enabled.

Game looks really good otherwise and everything is scaled properly.

This issue isn't super important as the game is more than completable without any game breaking bugs/glitches.