Rect lights cause visual noise on the light rendered when using raytracing. It is easier to see when you get rid of all other light sources in the scene. I have attached an example project.

This seems related to UE-68247.

Found in 4.23.1. CL#9631420
Reproduced in 4.24 P1 CL#9979423, 4.25 Main CL#10098181

Steps to Reproduce

1. Create a new project with raytracing enabled.
2. Set RHI Default to DX12 and enable raytracing.
3. Restart the project.
4. Place a sphere and a cube in the level.
5. Place a Rect Light next to each mesh.

Expected: The light renders properly

Result: There is visual noise in the render.

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By Design
ComponentUE - Rendering - Lumen
Affects Versions4.
Target Fix4.25
Fix Commit11745074
Main Commit11784623
Release Commit11745074
CreatedNov 12, 2019
ResolvedFeb 28, 2020
UpdatedSep 19, 2021