Engine Version: UE 5.8
Quality Setting: Medium (sg.GlobalIlluminationQuality=1, Lumen Lite / Irradiance Final Gather)
Platform: Windows (packaged build & PIE)
Core issue:
Under Medium quality, multiple shadow and lighting artifacts appear. The editor viewport shows minor glitches, but PIE and packaged standalone builds make them significantly worse and fully reproducible. High/Epic quality is unaffected.
Symptoms:
- Black ring / black patches on mid-distance trees when the aircraft does a sharp 180° turn. Flying forward restores the far distance, but a new black ring appears at mid-range.
- Shadow update lag — indirect lighting takes multiple frames to catch up after fast rotation.
- False shadow blobs on the ground under moving objects (a drifting car leaves irregular black blocks that stick to the terrain).
Hello there @1876141237!
Checking around the community, this scenario has popped up in similar threads. The problem here is that setting GI to Medium will force Lumen to use Software Ray Tracing only, which is quite good for performance, but prone to these kind of hiccups during fast camera changes.
Still, there are a few values to tinker here, please test the following cmdlets for your build (either run them manually from console, or add them to your DefaultEngine.ini file):
-
r.LumenScene.Radiosity.UpdateFactor 1.5 (allows more radiosity updates per frame, the Medium setting has this quite low)
-
r.Lumen.ScreenProbeGather.Temporal.MaxFramesAccumulated 10 (decreases blended frames in Lumen, which should lower the ammount of artifacts on scene)
-
r.Lumen.ScreenProbeGather.RadianceCache.NumFramesToKeepCachedProbes 15 (stale shadow data will be purged faster)
If the issue persists even with these settings, I would also test the High setting, while forcing a reduced value for the radiance cache, using r.Lumen.ScreenProbeGather.RadianceCache.NumProbesToTraceBud 100 (the default setting is 150, you can experiment with lower values).
Also, please make sure to check the associated UE docs for Lumen Lite: