Vulkan: Shadow gridlines with external lightmap and higher >24(?) lightmapscale/q3map_lightmapSampleSize

[videoP]

This has happened to me on several maps where I have used higher lightmap (worldspawn) and q3map_lightmapsamplesize (shader) values. It did not happen when using 8, it has happened when using 24. I'm still testing to find the exact cutoff and if this is the actual cause. The behavior does not happen on rd-default. MJT mentioned it might be something related to mipmapping the external lightmap image. I confirmed it happens to at least two other people as well. This is my lightmap compile: [light] -lightanglehl 1 -style -faster -fastgrid -cheap -cheapgrid -dirty -dirtgain 0.875 -dirtdepth 2 -dirtmode 0 -dirtscale 2 -bounce 3 -bouncescale 1.5 -fastbounce -bouncegrid -nobouncestore -samplescale 1 -super 2 -filter -patchshadows -nocollapse -nolightmapsearch -lightmapsize 4096 -debugsamplesize "[MapFile]"

I've attached a stripped down version of the map that shows the issue: mapBuggedLightmap.zip

Operating system and version: W10 22H2

Description of the bug (and if possible, steps to reproduce the bug):

What did you expect to happen instead? Expected same behavior as default renderer (no shadow lines)

[JKSunny]

@videoP, Thanks for detailed information and map, I'll look into it when I've got the time.

[JKSunny]

@videoP

Just commited a possible fix, please test

[videoP]

Seems fixed, awesome!

[JKSunny]

Nice, thanks for the bug report. Closing this now