Unreal Engine Issues
Unreal Engine Issues
Motion blur artifacting in MetaHuman Crowd demo
UE - Rendering - Features - Sep 10, 2026This issue was reported by a licensee and we also hit it during dev work on the crowds demo. It seems that this may be a general issue with motion vectors and teleporting actors as there are variou ...
SplineMeshComponent resources leak
UE - Rendering - Features - Aug 3, 2026A race condition occurs in the InitSplineVertexFactory_Internal }}function call, which is distributed across multiple threads. This causes {{FSplineMeshVertexFactory to be instantiated multiple time ...
Brick Pattern Artifact in Volumetric Clouds
UE - Rendering - Features - Jul 28, 2026A licensee has reported seeing a repeating brick-like pattern in volumetric clouds when they overlap with very distant geometry (or at the transition between nearby and distant geometry). The artifa ...
VSM shadows are missing for non-Nanite meshes in a PPV where Megalights is disabled, but Megalights is enabled in the project
UE - Rendering - Features - Jul 14, 2026In UE 5.8 r.Visibility.LocalLightPrimitiveInteraction mode 2 (enabled if MegaLights is disabled) was added and made the new default as a performance optimization. However, this causes shadows to d ...
Translucent meshes randomly flicker when using VSM
UE - Rendering - Features - Jun 23, 2026Flickering can occur on translucent materials, usually in the distance when there is at least one directional light and when using VSM. Flickering seems highly dependent on framerate and timing. L ...
Raytraced Hair Lighting using Light Functions atlas and positions the Light function material doesn't render correctly
UE - Rendering - Features - Apr 9, 2026Light functions don’t render on grooms when using ray traced shadows and positions in the light function material. The setup:A light (point/rect/spot) pointing to a groom hair system. The light's ...
Issue with r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat
UE - Rendering - Features - Mar 30, 2026When "r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat=1", some values for the Sky Atmosphere at some directional light angles can lead to the sun disk being cut off, and taking on a chord shape. A ...
New material translator: Switch statement not derivative aware
UE - Rendering - Features - Jun 13, 2025Analytical Derivatives are not calculated properly when using UMaterialExpressionSwitch. Disjoint UVs in screen space result in large jumps in the derivatives, which can cause artifacts as the wrong ...
Collision Drawing in Cooked Builds (Development) doesn't Show Geometry for Nanite Meshes
UE - Rendering - Features - Jun 2, 2025Context The showFlag.CollisionVisibility 1 cvar is a viewport visualization mode that highlights which Actors will block visibility. The showFlag.CollisionPawn 1 cvar is a Player Collision viewmode ...
Memory leak in distance fields with bDisableWorldRendering
UE - Rendering - Features - Apr 17, 2025There is a memory leak in the Distance Fields category when a mesh continuously moves through the world and the scene is being captured with bDisableWorldRendering set to true. This issue occurs on ...