thanks to epic games for new [Generate lightmap UVs] 4.23

[NasteX]

@YujiangW

I’ve done multiple small improvements to both auto lightmap UV generation and Lightmass in 4.23. They work together to remove dark corners/borders.

Auto lightmap UV generation:

• Correctly consider the 2 texel padding when generating lightmap UVs. They are there to ensure no leaking between lightmaps packed together.
• The bugged lightmap UV packing algorithm is fixed now. It was generating overlapped UV charts even for the simplest cube.

Lightmass:

• The ‘representative surfel’ method used by Lightmass to process each lightmap texel has been improved to mitigate dark corners (see FStaticLightingSystem::AdjustRepresentativeSurfelForTexelsTextureMapping() ). Basically it now tries to push the samples outside if it detects a wall. Sometimes it still fails however it should make most of the cases much better.

Amazing! Thank you for the improvements! We needed those things fixed for a long time.