Hi,
Has anyone had this problem of strange artifacts after conversion of a scene from 5.3.2 to 5.4.1? What might be causing this? I’ve been through a lot of testing and I still have no idea what the problem might be. I would be grateful for any help.
could you add a snapshot/recording of it in motion? not sure wth this.
The problem disappears when I switch to nanite on each mesh. But this is not the solution. After switching to nanite, I have strange ‘floating’ lighting, as if light is being generated in certain places. I don’t remember having this problem in 5.4. I only noticed it after the 5.4.1 hotfix.
I would check if this problem occurs in 5.4, but unfortunately this version can no longer be installed without a hotfix 
Edit: Unfortunately, the problem also occurs on 5.4 without the hotfix 5.4.1
Hi glitchered,
Ok, I decided to take a simple scene created in UE5.3 and then converted to UE5.4.1 to further demonstrate the problems with Lumen in UE5.4.1. The scene contains 4 meshes, a basic lighting setup, two additional RectLights and a simple base material. I have attached both scenes to the message below. In UE5.4 the scene contains errors in the lumen display. Disabling Support Hardware Raytracing in the Project Settings will remove the artefacts, but of course at the cost of disabling Lumen. Another solution is to change the mesh to Nanite. This will remove the artefacts but does not solve the problem. Another problem is the Two Sided option in the materials. Turning it on causes problems with the display and generation of Lumen, as I show in the attached video. The view from the camera, on the other hand, eliminates the problems.
okay. well… i noticed a certain directionality of the issue. i dunno how the tangent basis in unreal looks and works. but… i replaced all the meshes with simplifcations (without the bevels) and it fixed it.
to verify… i exported and reimported all 5 meshes with recomputed normals and it fixed it, partially, too. it now generates artefacts on the floor where the holes are in the walls.
and… well… all those holes have bevels on it. distance fields should be fine dealing with micro geometry but i reckon lumen meshcards are generated with some form of faulty directional data producing the artefacts. i dunno howto debug view this, but it’s an educated guess.
could be the same cause for the double sided material issue. it possible it traces in random faulty directions and potentially thru geometry, showing as random light leaks.
that’s all i can observe here. for proper technical debug you may have to wait for staff or a more advanced graphics dev to pick it up.
Hi,
It seems like indirect capsule shadows are broken in 5.4. Indirect capsule shadows are an UE4 feature for casting indirect shadows using capsules for characters and distance fields for static meshes.
I’m curious why did you enable it, as in your project I see Hardware Ray Tracing, Lumen and Hit-Lighting which should make it irrelevant.
In order to disable it and fix the artifacts - either uncheck “Distance Field Indirect Shadow” on your static meshes or switch off the entire feature using r.CapsuleIndirectShadows 0.
I’m starting to understand where this bug came from. I was getting the problem mainly in scenes that were converted directly from the previous version of Unreal. These scenes often contained elements from other scenes with the “Distance Field Indirect Shadow” option enabled, which is why the bug didn’t appear on all meshes in the scene. When importing fbx directly into UE5.4, the “Distance Field Indirect Shadow” option is disabled, so everything is fine. The problem turned out to be very easy to solve. Thank you very much for your help 
Hi @Thom_Coffee,
Thanks for reporting these artifacts. We have tracked down the cause of this issue and it will be fixed in UE 5.4.2.
Disabling “Distance Field Indirect Shadow” on static meshes is still recommended when using Lumen to avoid over-occlusion.
