Glitched lightmaps after long bake (some objects, sometimes)

Hello everyone

Although I can easily find many topics about lightmap problems, I couldn’t find anything related to this.

This is what I find this morning after a 5 hour long bake in production quality (100 bounces, scale 1, quality 6, smooth 0.9 - no .ini tweak). But yesterday I did 4-5 total bakes in preview/medium quality and this doesn’t happen.

As the tittle says, sometimes, some object(s) will be glitched like this (not in all bakes), and I don’t know why, while the UV unwrap is not ideal, it’s not overlapping and has worked before, many times (Let’s say I’ve baked that same object more than 40 times and it’s the first time it shows up like this).

I had a situation where I had one object that would always get glitched like this, even though the unwrap seemed fine, it wasn’t and I had to change and reimport the asset.

If I bake the whole scene again (which I will), probably this will disappear, this is somewhat annoying in preview/medium builds, but when it gets to production… it’s never finished until I get it right.

Could someone help me understand what is happening here and how can I avoid it?

Thank you in advance!

PC Specs:

  • i7-5960X @3.00GHz
  • 64GB Ram
  • GTX1080
  • Win 10

About the project:
This is a big Arch viz scene with several apartments each with its unique decoration items (2 at this stage), the walls and floors are made with simple geometry but the scene has many objects with higher polycount than what it should be. I’m being very conservative with the sizes of lightmaps only with the largest floors/walls/ceilings having 1024 resolution, everything else 512 and under. Original geometry for apartments came from a BIM file, a careful cleanup was necessary but it was mostly focused on the interior walls and so on.

I might have found something related Here, I don’t think I got this issue the same way, but I noticed I had a similar warning. I will confirm once the test bake is done.

Hey Valthrudnir,

So your project and its associated contents seems pretty far into its development, so reproducing this in order to determine what could be happening on my end is going to be difficult. What I can do is provide you with the resources to figure out how to resolve your issue.

Lighting Troubleshooting Guide

Aside from this guide, you will need to simply use the tools we have built in to visualize and debug what could be causing this issue.

Thank you,

Hei Andrew, my mistake, I forgot to mark it as solved, because I found the solution for this one, by re-importing meshes with different material slots, the
material override function in the mesh settings was on (the mesh had 4 material slots and then I removed one if I recall correctly). So it had 2 materials overlapping or something, mixing two lightmaps.

Thank you for your input though :wink: