Lumen shadow not appearing around object

JamesCurve · May 15, 2025, 5:06pm

I’m experiencing a strange lumen issue that presents in shadows. It appears that objects either in or in front of shadows cause lumen to not be able to see “behind” the object. In the example you can see that this is causing Lumen to effectively not resolve the shadow in a halo around the rear of the tire.

All lumen GI settings have been maxed in the PPV, along with the mesh having nanite both turned off and on with no effect. The distance field resolution of the tire has been tested at 100 with no change.

Any help would be greatly appreciated

ZacD · May 15, 2025, 7:29pm

Check the lumen debug view. You might need to make the car parts static meshes instead of skeletal meshes.

joshbridger · May 16, 2025, 12:44pm

Did you solve this?

JamesCurve · May 16, 2025, 1:20pm

Not yet, the wheels are static meshes. Replacing with skeletal mesh didn’t work

I’ve played around with so many CVars related to DFAO and Lumen, and yet none seem to make a difference

comlys · May 16, 2025, 5:16pm

What does the Lumen debug view look like? Any clues there?

JamesCurve · May 19, 2025, 1:46pm

Hi Shaun,

Sadly no clues in all Lumen debug views

I’ve overlaid them all in Photoshop and nothing seems to show any mesh bounds being read beyond the actual tire boundary. My initial thought was that it was a surface cache issue, but these screenshots seem to show it isn’t.

This is appearing in the most up to date 5.5 version

comlys · May 21, 2025, 3:10am

Can you try and disable Screen Traces for both GI and reflection?

JamesCurve · May 21, 2025, 9:25am

Hi Shaun,

Below is a screengrab with screen traces disabled for both GI and Reflections, seems like no change

By increasing screen percentage to 200, it will reduce the effect, but obviously this isn’t conducive to performance. Below screengrab shows 200%

I could migrate the file up to 5.6 Preview to see if that has an effect?

comlys · May 23, 2025, 5:30pm

Maybe it’s short-range AO. Can you try and toggle the showflag to see if it disappears?
ShowFlag.LumenShortRangeAmbientOcclusion 0

If so maybe dial:
r.Lumen.ScreenProbeGather.ShortRangeAO.ScreenSpace.SlopeCompareToleranceScale 0.9