Unreal Engine Issues
Unreal Engine Issues
Megalights support for anisotropic materials
UE - Rendering - Graphics Features - Lumen - Apr 14, 2026A licensee noticed that SUPPORTS_ANISOTROPIC_MATERIALS is not passed to FShadeLightSamplesCS::ModifyCompilationEnvironment for MegaLights ShadeLightSampleCS. Adding it fixes the issue. ...
Reflections of Masked Materials incorrect with Lumen HWRT and Max Refraction Bounces > 0
UE - Rendering - Graphics Features - Lumen - Dec 18, 2025Lumen HWRT Reflections of Masked Materials are incorrect when "r.Lumen.Reflections.HardwareRayTracing.Translucent.MaxRefractionBounces" is greater than 0. The same issue occurs if the Post-Process V ...
Lumen reflections break when the normals don't match the pixel depth information.
UE - Rendering - Graphics Features - Lumen - Oct 23, 2025Lumen Reflections can leave black spots in chrome materials with strong normals. Also tested on UE 5.5, CL: 41545209 and UE 5.6, CL: 45232827 ...
Light Leak Issue in Modular Buildings (Lumen HZBTraversal)
UE - Rendering - Graphics Features - Lumen - Oct 14, 2025Starting in Unreal Engine 5.6, disabling "r.Lumen.ScreenProbeGather.ScreenTraces.HZBTraversal" can lead to light leaking between adjacent or overlapping meshes. Also tested on Release-5.6, CL: 4523 ...
Incorrect Lumen Scene direct lighting when objects behind masked landscape
UE - Rendering - Graphics Features - Lumen - Oct 5, 2025When objects are placed behind or beneath a masked landscape and r.Lumen.HardwareRayTracing.SurfaceCacheAlphaMasking is enabled, the direct light evaluation is incorrect. There are two workarounds, ...
Lumen Translucency lighting vs opaque mismatch is larger than expected
UE - Rendering - Graphics Features - Lumen - Sep 5, 2025The licensee's VFX team has been struggling with getting their Niagara systems with translucent materials to fit into the environments they are being used in. In a project with default settings, the ...
Lumen Card Sharing is active on material with custom primitive data
UE - Rendering - Graphics Features - Lumen - Aug 13, 2025The wrong emissive value may be used on Nanite objects with custom primitive data when Lumen card sharing is enabled. This issue can be mitigated with: r.LumenScene.SurfaceCache.AllowCardSharing 0 ...
Crash when displaying lumencards on map with many objects
UE - Rendering - Graphics Features - Lumen - Aug 1, 2025There is a thread conflict between FRDGBuilder execution in Background Worker and LumenVisualizer's LumenCard add/delete process. When lumen cards are displayed in a scene with many objects, a crash ...
Hardware Raytracing on Lumen can cause a crash on AMD Radeon GPUs
UE - Rendering - Graphics Features - Lumen - Jul 29, 2025Hardware Raytracing support can cause a crash on AMD Radeon GPUs when creating the RT pipeline state. ...
Niagara mesh particles invalidate lighting when "Cast Shadow" is enabled with Hardware Ray Tracing enabled
UE - Rendering - Graphics Features - Lumen - Jun 24, 2025Lumen HWRT, combined with Niagara Mesh Renderer, can cause the Lumen Scene to be reset, resulting in a sudden change to indirect lighting. ...