Context
Lumen is the default global illumination and reflections system. Lumen renders diffuse interreflection with infinite bounces and indirect specular reflections in large, detailed environments at scales ranging from millimeters to kilometers.
Problem
The problem is Lumen ignores Landscape Visibility holes when Hardware Ray Tracing is enabled and the Ray Lighting mode is set to Surface Cache.
The current workarounds are either disabling Hardware Ray Tracing by entering "r.Lumen.HardwareRayTracing 0" into the console command line or changing Ray Lighting mode, in project settings and searching for lumen, to "Hit Lighting" or "Hit Lighting for Reflections".
1.) Download and open repro project uploaded in ticket (internal available only)
2.) Ensure level "Landscape_Map" is opened (should be opened by default when opening project), if not go to Content Drawer > Content > Landscape_Map
Observe: Hole in green hill landscape
3.) Change view mode to Lumen scene by going to Lit > Lumen > Lumen Scene
Observe: Hole in green hill landscape disappears
Expected: Hole should still exist and be taken into account by lumen scene
Note: If the hole is still there when switching to Lumen Scene, ensure Hardware Ray Tracing is enabled by entering "r.Lumen.HardwareRayTracing 1" into console command line
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-241482 in the post.
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Component | UE - Graphics Features - Ray Tracing |
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Affects Versions | 5.5 |
Target Fix | 5.6 |
Created | Jan 31, 2025 |
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Updated | Feb 12, 2025 |