Texture resizes w bilinear filtering

[Richard-L]

I had brought this up before, so I hope it's okay to post something I observed:

See how Duckstation/TR2X change from nearest neighbour to bilinear filtering (no edge blending).

DS

2025-01-11.23-41-24.mp4

TR2X

2025-01-11.23-42-13.mp4

Sadly TR2X is resizing the textures. TR textures are bad enough, and the super low-poly environments they're on don't help them. Their seamlessness is very hit or miss, to put it lightly. So to further damage this by resizing the textures (when filtered), seems quite costly to me.

If there's anything that can be done to reach Duckstation's no edge blending filtering, I think it would be worthwhile.

[rr-]

For the record this is OG PC behavior.

Normally we could fix this using GL_CLAMP_TO_EDGE, but the problem is the game uses texture atlases which produces bad artifacts with the bilinear filter on. The solution is to add a fake border around each texture.

Ref:
https://stackoverflow.com/a/35119455
https://gamedev.stackexchange.com/a/61800

This could potentially also help with the anisotropic filtering.

There are two ways I can imagine we could go around this.
The first is to literally offset all texture UVs and add those pixels by hand. It'll require us to support non-256×256 texture pages and has unknown performance hit on level loading.
The other is to use shaders, but this has an unknown performance hit on rendering which is already strained. I think Duckstation implements this here: https://github.com/stenzek/duckstation/blob/ce0689687c58020e9fd45bc3c6b0053b988b63b4/src/core/gpu_shadergen.cpp#L69-L96

CC @lahm86

[lahm86]

I know that TombEditor generates padding around every texture, so whichever pixel is at UV bounds gets repeated. But as you say this means 256x256 tiles become inefficient with lots of dead space.I agree, shifting everything in OG would have a big impact on loading for sure. Texture packing is fast when we're just appending bits and pieces to end tiles, like for injections, but rebuilding the entire set on the fly is another story.
I personally feel it looks fine as is and is in-keeping with OG PC. But appreciate that there is a request for change.