Tiled artifacts with smoke

[slipher]

Some of the light tiles are seemingly poking holes through the smoke. The bug does not happen if setting r_drawDynamicLights 0. Happens with both 0.55.0 engine and a recent engine.

The tiled realtime light renderer has a known limitation with non-depth-writing textures since it filters out lights if they are out of range according to the depth buffer. We could try to blame it on that (if the grate textures are non-depth-writing), but I don't think that could explain why the smoke is not visible at all in some spots.

[VReaperV]

It's possible that the lights are added in those spots but the blending modes make the result look weird.

[slipher]

I tried setting attenuation = 0.0; in the computeDynamicLight GLSL function. Having lights with 0 intensity ought to be the same as having no lights, but the same artifact is produced. So there must be a real bug.

[slipher]

In fact it DOES happen with r_drawDynamicLights 0. Must have messed up the previous test somehow. After fixing r_showLightTiles, I see that the light tiles are bigger than the squares I'm getting here here. And there aren't even any dynamic lights being rendered in the messed up area. So nothing to do with dynamic lights. Tile-patterned artifacts can happen with various driver/GPU bugs such as in #949

[slipher]

Doesn't happen for me with Intel or Nvidia proprietary drivers.

Easy repro steps:

• devmap uvcs
• setviewpos -2242 -1267 184 177 -27
• testshader gfx/weapons/rifle/smoke or testshader gfx/buildables/acid_tube/spore

The triggering condition for the foreground shader is use of depth fade. I haven't investigated yet what needs to be in the background.

[VReaperV]

This seems to be happening in front of surfaces with alpha-test? Might be worth trying to visualise the depth buffer.

[VReaperV]

Btw does switching relief mapping affect it in any way?

[slipher]

It happens in both ultra and low presets so does not depend on relief mapping setting.

[slipher]

The depth value as read in the generic shader with depth fade enabled, with the color formula 1 / (1.0001 - depth) / 600.

I don't think those low values are really written to the depth buffer as I can put a model in front of there and it displays fine. But wrong values are read out by the shader. Maybe there is some bug with not maintaining a consistent view of memory.

[VReaperV]

I don't think those low values are really written to the depth buffer as I can put a model in front of there and it displays fine. But wrong values are read out by the shader. Maybe there is some bug with not maintaining a consistent view of memory.

Does it happen to use bindless textures? That's the only issue I could think of right now.

It does also look like a tiling pattern you might get with rasterisation, so it might just be that it hasn't finished writing to the depth buffer yet for some reason. Could be worth trying to add glFinish() or glMemoryBarrier( GL_ALL_BARRIER_BITS ) after the relevant drawcalls and seeing if it changes anything.

[slipher]

Happens regardless of bindless texture (or material system) settings.

I tried putting glMemoryBarrier( GL_ALL_BARRIER_BITS ) in Tess_End and that didn't fix it.

Since I didn't note the GPU model yet it's AMD Radeon RX 7700 XT. Mesa 22.3.6

[VReaperV]

I guess it's just a driver bug then.