I spotted something interesting in the current ue5-main branch (upcoming UE 5.5):
=> git commit: Initial Lumen support for DynamicMeshComponent
I did a couple of tests, and it works (almost) like a charm. The idea is that they added new interesting settings for DynamicMeshComponent and Actor:
Draw Path: Static Draw | Dynamic Draw
Distance Field Mode: None | Async CPU Distance Field
So there is now the option to compute the dynamic mesh Signed Distance Field in an async way at runtime (vs. in the editor for Static Meshes), and this make the dynamic mesh fully compatible with lumen, both with software raytracing or with hardware raytracing.
In “Dynamic Draw” mode, Lumen only works with Hardware raytracing in Hit Lighting mode (meaning, SDF is not used at all, and the “Distance Field Mode” can be set to “none”).
Here is a simple result of a blue dynamic mesh box, lighted by a spotlight (ScreenTraces are disabled too, otherwise this could be faked by screen-space lumen attempts) :
Only issue I found is if the angle between the camera and the dynamic mesh is too broad (roughly > 90deg) lumen is disabled for the mesh. But this is nevertheless quite OK, and in particular when the reflected surface is occluded:
Possible answer to these earlier posts: