The faces seem to melt when changing View mode to Lumen Scene and Viewport Scalability to Epic. I tried in a vanilla project (Version 5.6.1) and is not an issue testing with the same character. Epic MetaHuman team was not able to repro either. MetaHuman team did an preliminary investigation and asked to submit EPS so they are able to dig deeper/ Share with others across their team. They suspect the cause to be coming from project settings.
Steps To Reproduce
1. Drag BP_Ada into an empty level
2. Change view mode to Luman Scene and Viewport Scalability to Epic.
Hello there, I would like to add some additional information to this case.
You can reproduce this behavior in Unreal 5.6 if r.RayTracing.Geometry.SkeletalMeshes.LODBias is set to anything higher than 0 , or use the Ray Tracing Min LOD as the Raytracing Performance Guide Recommends.
Exact repro steps:
Create a new Unreal 5.6 Metahumans Project
Open the Ada_FaceMesh SkeletalMesh asset
In the viewport open the Ray Tracing Debug>Triangles
In the viewport set the visible LODLevel to 0
Enter the console command r.Raytracing.Geometry.SkeletalMeshes.LODBias 1
Note the broken appearance of the face mesh
It’s important to note that there is this comment on the cvar in SkeletalMesh.cpp
TEXT("When non-zero, a different LOD level other than the predicted LOD level will be used for ray tracing. Advanced features like morph targets and cloth simulation may not work properly.\n")While I can understand if other LOD Levels may not function correctly, I would expect that subsequent LODs would not appear completely broken. When using a LODBias of 0, the LOD chain presents as expected at each LOD level. Are there any recommendations for keeping the integrity of a metahuman character without morph targets while still benefiting from a SkeletalMeshLODBias during general gameplay?
Unfortunately after implementing the fix the problem seems to persist. We also tried this with a more recent editor version with Unreal 5.7.1 and it appears the be the same as well.
LOD0 in the raytracing scene will appear correct but after changing r.RayTracing.Geometry.SkeletalMeshes.LODBias 1 and modifying a rendering relevant property the character appeared like the examples I posted.
If you have other changelists that might be required for the fix please let me know and we’ll see if we can include those as well.
Hello, I believe there were two compounding issues. The first was fixed but the second produces similar results. I’ve submitted the second into UE5/Main here: 50718805. I confirmed locally that it fixes our repro. Hopefully that’s the last of it.
Hi Zachary, I’ve done some testing with both of those preports. I’m seeing different behaviours however the raytracing mesh appears to still display some deformation issues.
In this case I was able to show the same issue on the Ada metahumans character using r.RayTracing.Geometry.SkeletalMeshes.LODBias 2
The static pose appears correct but applying some animation assets displays a very deformed result which will show raytracing inconsistencies.
Please let me know if you are able to reproduce this with a metahuman character with an animation sequence applied. If you have any other leads, it would be appreciated. Thanks!
Hello Zachary, thanks for the follow up on this issue. We reviewed your fix in this changelist and put all of the updates together. We’re seeing promising results in editor, and will keep you update you as soon as we’ve completed our testing.