Title: UE 5.8 – Skeletal Meshes lose shadows with MegaLights at GI Medium (fix)
In UE 5.8, Epic added some new CVars to the scalability settings. As a result, Skeletal Meshes are no longer represented in the Global Illumination – Medium preset.
This causes odd behavior with MegaLights: Skeletal Meshes don’t cast shadows. My guess is that this happens because MegaLights replaces the default shadow generation, so the fallback shadow aren’t working with MegaLight enabled.
With MegaLight enabled and Global Illumination Scalability at Medium:
Temporary fix (current session only)
Run the following commands in the console:
r.RayTracing.Geometry.SkeletalMeshes 1
r.MeshCardRepresentation.SkeletalMesh 1
With GI set to Medium and MegaLights enabled, Skeletal Meshes will cast shadows again. However, these values only last for the current session.
With MegaLight enabled and Global Illumination Scalability at Medium & quick fix:
Permanent fix
Edit BaseScalability.ini, located at:
UE_[Version]\Engine\Config\BaseScalability.ini
For example: C:\Program Files\Epic Games\UE_5.8\Engine\Config\BaseScalability.ini
At the end of the [GlobalIlluminationQuality@1] modify:
r.RayTracing.Geometry.SkeletalMeshes=0
r.MeshCardRepresentation.SkeletalMesh=0
by :
r.RayTracing.Geometry.SkeletalMeshes=1
r.MeshCardRepresentation.SkeletalMesh=1
Restart the engine and now Global Illumination Medium with MegaLight enabled, SK will have proper shadows.
In GI Medium:
In GI High:
Performance note: These CVars in the Global Illumination Medium preset ([GlobalIlluminationQuality@1]) were added by Epic for a reason, most likely for performance reasons. Be aware that enabling Skeletal Mesh representation in GI at Medium will increase both CPU and GPU cost.
A cleaner fix would be a proper shadow fallback for Skeletal Meshes when MegaLights is enabled. However, I suspect that would require engine modifications, which is well above my pay grade.