Epic's GPUlightmass

Development Rendering
426

I also noticed that when I was testing your scene, and that is basically a ray offset issue - to avoid the decal mesh blocking light the ray origin needs to be pushed away so it starts in the front of the decal. There are two ways to do that

  1. Move the decal closer to the ground (by reducing its Z position by a fraction)
  2. Modify LightmapPathTracing.usf
Ray.Origin += max(ShadowTerminatorFix ? ShadowOffset : BaseOffset, RelativeOffset * 100) * Normal;
Ray.TMax -= length(max(ShadowTerminatorFix ? ShadowOffset : BaseOffset, RelativeOffset * 100) * Normal);

You can bump up the * 100 to 200 or something and restart the editor to see if it resolves the issue. I believe it could be good if ray bias is included in GPULM settings at some point in the future.

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