Emissive material missing reflection / indirect lighting in UE5.1 using Lumen

[kharnholio1]

Hello everybody,

I have a strange phenomenon where an emissive material works fine when applied to a mesh or primitive objects (cube / plane) but not so much on another specific mesh. The reflected and indirect light is most times not visible or very faint, regardless of the distance to the camera. The parts of mesh 2 which are not visible in screenspace seem to emit even less light.

The current setup and latest tests I have made:

• “Engine Scalability Settings” are all on Cinematic

• “Dynamic Global Illumination Method” Lumen

• “Reflection Method” Lumen

• “Reflection Capture Resolution” 2048

• “Support Hardware Ray Tracing” true

• “Min Screen Radius for Lights” reduction to 0,01 (default 0,03) did not help

• “r.LumenScene.DirectLighting.MaxLightsPerTile” does not seem to have an effect

• Scene is setup in real world scale

• Both meshes have the same material applied

• Both meshes seem to be correctly enclosed

• Both meshes normals are facing the correct direction

• Both meshes are set to “stationary” as the material color can change, but also neither “static” or “movable” had an effect

• Both meshes are set to be “Emissive Light Source”

• Both UV spaces look similar dense

Does anynone have a clue what might be the cause of this?

[ZacD]

Have you checked the lumen debug views under lit? Does the mesh have distance fields enabled on them?

[kharnholio1]

Good idea,

although I do have mesh distance fields activated for the project (Voxel Density 0,2) the Lumen debug view does not show anything strange, or does it?

[ZacD]

That looks like the nanite debug views, not the lumen ones where you’ll see the surface cache and how the lighting is being evaluated.

[kharnholio1]

ARGH! Yes you are right here is the Lumen Overview: