Hi there!
I’m running into a persistent flickering issue with my skybox in Unreal Engine 5.6.1, and I’ve exhausted a bunch of troubleshooting steps. Hoping you or the community might have insights.
Setup Details:
- Using a custom skybox with a translucent material (for a transparent sky using unreal’s default sun and atmosphere).
- Main light is a Directional Light acting as the sun, with Virtual Shadow Maps (VSM) enabled for shadows.
- Lumen is active for global illumination.
- The skybox is a large dome/mesh enclosing the scene, with some internal lights (e.g., spotlights) placed inside it.
Problem:
The skybox starts flickering intensely whenever there’s at least one spotlight active in the scene, especially when the spotlight’s rays intersect with the sun’s directional light and the skybox is in the player’s view. It seems tied to shadow interactions – if I disable the spotlight or remove shadow casting, the flickering stops, but that’s not ideal for my lighting setup. This happens even with only 1 directional + 1 spotlight; no other lights exacerbate it further.
What I’ve Tried (No Luck So Far):
- Increased shadow-related console commands like r.Shadow.Virtual.MaxPhysicalPages to 8192 and r.Shadow.Virtual.ResolutionLodBiasDirect to higher values.
- Enabled and debugged shadow frustums (via stat shadowfrustums) – flickering persists when shadows overlap.
- Tested on high-end hardware (RTX 5090) and lower-end PCs to rule out GPU/memory issues.
- Checked world positions (player/skybox below Z=0) – not the cause.
- Adjusted light properties: Made lights stationary, tweaked shadow bias/resolution, disabled Lumen temporarily.
- Ensured no overlapping geometry or material issues; skybox material is set to translucent with proper blending.
At the skybox material, going to Translucency > Lighting mode > Surface ForwardShading solves the problem. But it’s too heavy for a skybox and it looks like glass with this option, which is bad.
This only triggers with VSM + spotlight + directional intersection visible on the skybox. Any ideas on how to solve this glitch @EnduringStephenK ??