Inexplicable artifact after baking GI.

Unity Engine
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1

Hi!

I’m having a major issue. I’m trying to bake my scene, but I’m encountering artifacts in a specific area. It looks like I have UV overlaps, but that’s not the case. I’ve correctly unwrapped my UVs, and my mesh only has one UV to ensure proper mapping. I even generated the lightmap UVs in Unity with large padding, but that didn’t solve the issue. When I tried baking without the spiral stair, the result was correct, so I’m not sure why the stair is causing problems with the GI baking.

I’m in URP on Unity 2022.3.7f1

Unity ligthmapping generate from mesh :

With my uv :

2

These looks like texel validity artifacts (happens when rays hit exposed backfaces). Please see chapter 15 of our troubleshooting guide for how to deal with it Lightmapping Troubleshooting Guide

3

Likely the underside of your stairs steps have exposed backfaces, or something like that

4

Yes it’s the stairs step, they are made like that :
https://gyazo.com/60f69b9c1fd9074295a98aa20885ba0d

In you documentation in 15.2.3 Enable the Double-Sided Global Illumination material property i dont see any double sided GI in my material i’m in URP
https://gyazo.com/8e27db1dd02a700a74104e18c6ca9b51

EDIT ! I used a custom shader that renderer in double sided, i switch to lit standard in that fix my issue thanks !

5

As far as I remember, in URP’s default shaders, the Double Sided GI flag is controlled internally based on what “Render Face” option you have set. Render Face = Both means Double Sided GI is enabled.