Vulkan: Add MMPX upscaling texture shader

[unknownbrackets]

See https://casual-effects.com/research/McGuire2021PixelArt/index.html - this is just a very straight forward port.

I think we could at some point use a #define or option in the ini to have the shader produce more than 1x1, perhaps by exposing a function like writeScalingu() that calls imageStore/buf2.data based on an x/y.

But for now, we can easily add this option. I think I got the 4 pixels right, works for me at least.

-[Unknown]

[hrydgard]

Awesome!

I think it could also work as a post-processing filter, but it might be too unstable/flickery?

[hrydgard]

Hm, something is not quite right (Cave Story):

[hrydgard]

Now we're talking!

[unknownbrackets]

Oops, I changed the bottom quickly afterward and did it backwards. My bad.

But it still looks bad at 3x upscale, I guess because it's making uneven decisions?

-[Unknown]

[hrydgard]

yeah, this is only gonna work for 2x. Maybe repeated application for 4x but I doubt that will be great.

[unknownbrackets]

Right, because its decisions aren't consistent then. I think 4x looks fine, because the decisions are consistent again. I guess the best thing would be to lock it to 2x or something in the ini...

-[Unknown]

[hrydgard]

Yeah, adding a lock is probably a good idea.

[unknownbrackets]

Added a simple limit option. Doesn't affect UI, so it does mean they can select 3x and it will just actually use 2x. But low memory does that too (which btw, still gets reported regularly...)

-[Unknown]