I’m having an unreasonable increase in lightmass build times when I use 4k lightmaps.
Example from a very simple map (contains only directional light and two planes (2 triangles each):
2k lightmaps: 11 min build time
4k lightmaps 3h 16 min build time.
I have 48 Gb RAM so memory shouldn’t be an issue, and the geometry in this test has intentionally been kept super simple.
Any ideas about what’s going on here?
It’s only 18times more for 4 time bigger lightmaps. I can just guess that Lightmass has to do something that does not scale linearly per lightmap texel. Or it might just be cache misses. In any case you probably don’t need that big lightmaps.
Use the statistics window to see what meshes were taking the longest to calculate for the build. That can help you sort this out and try to reduce your build times.