Description

Dark moving noise is visible in hair in the shadows when Lumen screen traces are active.  Example of noise when screen tracing is frozen:
[Image Removed]

Turning off Lumen screen traces using r.Lumen.ScreenProbeGather.ScreenTraces 0 causes a noticeable quality loss.

Modifying FLumenMaterialData InternalReadMaterialData_GBuffer(const FGBufferData GBufferData) so pixels with GBufferData.ShadingModelID == SHADINGMODELID_HAIR are considered as bHasBackfaceDiffuse, does stop screen traces for hair by going down the same path as foliage, however there is the noticeable quality loss.

Further changes would likely need to be made in other areas of Lumen similar to what was done for foliage to maintain the quality.

Steps to Reproduce
  1. Open the sample project from the UDN in the Additional Info URL
  2. Observe the moving noise in the hair on the shadowed side of the head when up close

Expected

There is no moving noise in the hair shadows

Actual

The moving noise in the hair shadows is consistent and active as long as Lumen screen tracing is enabled

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Fixed
ComponentUE - Graphics Features
Affects Versions5.45.3.2
Target Fix5.5
Fix Commit33258050
CreatedApr 18, 2024
ResolvedApr 26, 2024
UpdatedMay 17, 2024
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