Starting in Unreal Engine 5.6, disabling "r.Lumen.ScreenProbeGather.ScreenTraces.HZBTraversal" can lead to light leaking between adjacent or overlapping meshes.
Also tested on Release-5.6, CL: 45232827
1. Download the attached test project
2. Repeat steps 3-6 in Unreal Engine 5.5, 5.6, and 5.7
3. Open the test project
4. Move the camera inside the white box (`BugItGo 7673.144965 -397.158112 3098.579393 -11.042047 499.235542 0.000009`)
5. Let auto-exposure settle
6. Run the console command "r.Lumen.ScreenProbeGather.ScreenTraces.HZBTraversal 0"
7. Observe in Unreal Engine 5.5, this produces no visible change. In Unreal Engine 5.6 and 5.7, this causes light leaking at the corners of the box.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-348884 in the post.
| 0 |
| Component | UE - Graphics Features - Lumen |
|---|---|
| Affects Versions | 5.6.1, 5.7 |
| Created | Oct 14, 2025 |
|---|---|
| Updated | Oct 15, 2025 |