Like you see on the attached files. What is the cause of it? Tried some commands, changing AA methods. There are also other light sources in the room and such…
Check the lumen scene debug views under lit, typically artifacts like this are from Lumen only working in screen space. Make sure the debug view looks like an approximate representation of the scene.
Hi! Thanks for reply. Can you explain a little bit more? How should I read this and do something with it?
Lumen relies heavily on the surface cache, with some screen space compensation as well. Bright spots on the surface cache will leak through and show up as artifacts and glitching. Make sure that walls are at least 10cm thick, but preferably 20cm or more. Try having walls, windows, doors, floors, etc, be separate modular pieces. And it’s not just the wall selected that will cause issues, the wall to the right with thin lines will cause problems too.
Ah! Got ya.
So I did have the modules. Now I’ve added thickness but nothing really changed.
There are also grayboxes outside the interior. If I delete them it’s just brighter but the same problems remain.
I’m seeing something similar in a scene I’m playing about with that was done in Twinmotion.
Not long started using Unreal Engine 5.1.1 & 5.2, I know Lumen has issues with mirrors but no idea why I’m getting the mottled effect all around the scene. I think it may be an issue with Lumen and the frosted glass?
Nope, it’s not the frosted glass as I changed it for plain glass and still getting the ghosting, even took the glass out altogether and that didn’t resolve my problem either. 
Generally this is what to expect in scenes with very little direct light. If you’re light is from an HDRI, try adding a real directional light and try to bring the overall direct light levels up if possible.
You have light leaking like crazy through your walls with the windows and you have tigerstriped lighting on the walls, usually caused by having a lightsource with a large source radius intersecting with a mesh.
Looks like a bunch of stuff has no distance field representation at all, including that cavernous hole on the right side.
Thanks for the answer 
But they do have distance field. I upscaled the resolution and voxel density but it didnt change a thing. Also no intersection as they’re modular. The only lightsource there is a directional light with a low source angle.
I’ve gone ahead and circled the problem areas for you so that you can work to narrow down the problem
Red: Light coming straight through the backfaces of the wall, either the mesh is too thin, is single sided, or there is some other problem
Green: Striped issue, generally a distance field problem (common with two-sided distance fields) or like I said, intersecting lightsource. But you say that isn’t happening here so…
Pink: Hole?
If you can clean up the scene to get rid of those issues, Lumen should behave better. With regards to the distance fields I would suggest checking the global distance field debug view, and make sure you aren’t using two-sided materials or generating two-sided distance fields.
1 Like
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.