Unreal Engine Issues

Hardware Lumen Surface Cache Artifacts on Nanite Geometry

When 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 ...

GPU Crash from out of memory read/writes in Lumen when using non-power-of-2 TracingOctahedronResolution

When 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 ...

DiffuseIndirect_Lumen_3 parameter missing and causing crash with Screen Space reflections and Lumen Async Compute

When the Reflection Method is set to Screen Space and Lumen reflections async compute is enabled Unreal will crash because DiffuseIndirect_Lumen_3 parameter missing, due to how DenoiserOutputs are o ...

Divergent group barriers in Lumen

Intel reported GPU crashes on their hardware caused by divergent group barriers in ScreenProbeConvertToIrradianceCS:[numthreads(THREADGROUP_SIZE, THREADGROUP_SIZE, 1)] void ScreenProbeConvertToIrra ...

NVIDIA 5080 GPU Crash when launching City Sample with DX12

UPDATE This issue no longer reproduces on driver versions 580.88 and higher. City Sample game crashes immediately upon opening with a NVIDIA 5080 with the latest drivers as well as some previous dr ...

Lack of multi-bounce when using software traced lumen radiosity

Certain Lumen Hardware Ray Tracing CVars, when disabled in isolation, will not fall back to tracing the Global Distance Field, because the Global Distance Field is still disabled. The function "Lum ...

r.Lumen.Reflections.DownsampleFactor split screen artifact

In Split-Screen, with "r.Lumen.Reflections.DownsampleFactor" set to 2, it is possible to have vertical colored artifacts on View 1 (the second view). The Licensee reported the artifact occurred on ...

Lumen temporal flicker after leaving Editor open for 3+ days

Lumen GI has temporal flickering/noise after running the Editor for 3+ days. ...

Lumen doesn't handle Area Lights Reflection Occlusion well

Lumen doesn't use correct sky light settings when GI scalability changes from Low to High

When the Global Illumination scalability settings are changed in the editor from High to Medium, they primarily act on the r.Lumen.DiffuseIndirect.Allow and r.SkyLight.RealTimeReflectionCapture.  No ...