keywords: UE5, Lighting, Lumen

The previous article: UE4 Lighting Notes

Optimization

Some parameters to reduce performance costs (also lose some effects):

r.Lumen.TraceDistanceScale=0.01
r.Lumen.DiffuseIndirect.MinSampleRadius=0.1
r.Lumen.DiffuseIndirect.VoxelStepFactor=10

Default:

r.Lumen.TraceDistanceScale=1
r.Lumen.DiffuseIndirect.MinSampleRadius=10
r.Lumen.DiffuseIndirect.VoxelStepFactor=1
Issue: Shadow flickering / glitch by Lumen (UE 5.0)

Solution: Try turn of RejectBasedOnNormal first (this switch has been turned off by default in latest version):

# Whether to reject history lighting based on their normal. Increases cost of the temporal filter but can reduce streaking especially around character feet.
r.Lumen.ScreenProbeGather.Temporal.RejectBasedOnNormal 0

If doesn’t work, then try turn on TemporalFilterProbes:

# Whether to temporally filter probe traces to reduce noise.
r.Lumen.ScreenProbeGather.TemporalFilterProbes = 1

If neither of the above works, try ReferenceMode last:

# When enabled, traces 1024 uniform rays per probe with no filtering, Importance Sampling or Radiance Caching.
r.Lumen.ScreenProbeGather.ReferenceMode = 1

Reference: UE 5 Early Access issue/glitch with my foliage
https://forums.unrealengine.com/t/ue-5-early-access-issue-glitch-with-my-foliage/239781/7

Tutorials

Lighting in Unreal Engine 5 for Beginners
https://www.youtube.com/watch?v=fSbBsXbjxPo

80 Level Ratings: 10 Excellent Tutorials on Lighting in Unreal
https://80.lv/articles/80-level-ratings-10-excellent-tutorials-on-lighting-in-unreal/

Documents

GPU Lightmass Global Illumination
https://docs.unrealengine.com/5.3/en-US/gpu-lightmass-global-illumination-in-unreal-engine/

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