Black Areas in Lightmap

atomander

Hi folks, pretty new Unreal user. I am trying to build the lighting in my scene, but when I do, get ugly black areas around some of my UV seams. Not sure why; no errors pop up when building the lighting, the second UV channel seems good with no overlapping areas and plenty of margin space. Any other ideas why this might happen?

alecchalmers

It's possible that it's being caused by your lightmap's UVs not falling in a pixel. When your UVs aren't snapped to the pixels and they cut through a pixel, the lightmap sometimes bleeds like this because the lightmap is telling Unreal to cut the pixel in half, which it can't do.

If this is the reason you just need to snap your UVs to the grid, it looks like you may have nudged a UV slightly and now it's off the grid?

World of level design does a good job of explaining it near the end of this article: http://www.worldofleveldesign.com/categories/udk/udk-lightmaps-03-how-to-fix-light-shadow-lightmap-bleeds-and-seams.php

synergy11

Sorry to jump in.

How does snapping LIght map UVS to pixels help with Organics I wonder? Like unwrapping an un even edged UV island. Should I align all the verts together in the UV editor even though this is incorrect workflow for Texture UVS, as doing this would distort and stretch the texture?

atomander

Thanks guys! I bumped up the padding on my islands in the lightmap UV channel and increased the lightmap resolution, and it went away!

alecchalmers

synergy11 wrote: »

Should I align all the verts together in the UV editor

I think it's a simple case of making sure you've turned on pixel snap. could be wrong. Don't worry about a really tiny bit of distortion though.

@atomander
Glad you got it sorted, I always forget that lightmap resolution is usually first port of call.