Description

The 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
or
r.LumenScene.SurfaceCache.DetectCardSharingCompatibility 0

Steps to Reproduce
  1. Create two Materials that outputs emissive data red and blue and uses a Custom Primitive Data node (or open the attached project's TestEmissiveCPD_Modified level)
  2. Enable Lumen scene overview so you can see the materials updating in the reflection view
  3. Apply the Material to several Nanite and non-Nanite spheres in the level
  4. Fly over the spheres

Expected
The correct emissive color is applied in the scene

Actual
When the camera approaches the spheres they sometimes use/share the wrong emissive color because of Lumen card sharing. This issue can be mitigated with:
r.LumenScene.SurfaceCache.AllowCardSharing 0
or
r.LumenScene.SurfaceCache.DetectCardSharingCompatibility 0

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Unresolved
ComponentUE - Graphics Features - Lumen
Affects Versions5.6
Target Fix5.7
CreatedAug 13, 2025
UpdatedAug 14, 2025
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