Unreal Engine Issues
Unreal Engine Issues
SceneCaptureComponent2D destroys shared Lumen Radiosity atlases every frame, breaking temporal accumulation in the main view
UE - Rendering - Features - Lumen - Sep 14, 2026A USceneCaptureComponent2D with bCaptureEveryFrame = true and default post process settings causes FLumenSceneData::IndirectLightingAtlas and RadiosityNumFramesAccumulatedAtlas on the sharedScene->D ...
Megalights support for anisotropic materials
UE - Rendering - 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 - 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 - 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 - 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 - 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 - 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 ...
Hardware Lumen Surface Cache Artifacts on Nanite Geometry
UE - Rendering - Features - Lumen - Sep 1, 2025When using Hardware Lumen with Nanite-enabled meshes in UE 5.6+, black / dark surface cache artifacts appear that result in generally darker and unstable lighting. These artifacts are not immediatel ...
Lumen Card Sharing is active on material with custom primitive data
UE - Rendering - 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 ...
GPU Crash from out of memory read/writes in Lumen when using non-power-of-2 TracingOctahedronResolution
UE - Rendering - Features - Lumen - Aug 6, 2025When the r.Lumen.ScreenProbeGather.TracingOctahedronResolution is not a power of 2 or LumenFinalGatherQuality in a Post Processing Volume is set to a value such that the TracingOctahedronResolution ...