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

Development Rendering
1

with this new build-in Generate lightmap UVs i am able to create lightmap for complex objects as this one

https://forums.unrealengine.com/filedata/fetch?photoid=1404134

2

As far as I know there, nothing has changed for that feature in that it still requires the mesh to have existing UV seams, meaning it’s not a completely automatic feature, it’s just an algorithm that flattens out existing UV’s

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very happy with 4.23 auto ganarated uv result

5

For a model like that cloth, it’s best to UV it before doing any cloth simulations.

6

Eh, if it works it works, yah?

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I don’t think that has anything to do with generate lightmap UV’s, it looks like it might just be a change to do with lightmap borders

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Yeah, as far as I know, the automatic lightmap UV generation has remained essentially the same since Unreal Engine 3, so it would be a bit weird for it to suddenly change significantly with no fanfare whatsoever. I’m wondering if maybe the incorrect results in 4.22 are actually due to a recent regression, rather than some fundamental limitation that has existed unaddressed for the past ten years.

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even in best of ue4 archviz we see this dark borders

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They removed the weird UV 2x2 pixel padding that was added automatic in the older versions. I am just guessing that this might be the change that happened for the lightmaps.

11

Big if true. I’ve always hated those dark grey edge borders on generated lightmaps they were a huge pain.

12

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.
13

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