Context: this report comes from a RenderFuzz-based UE 5.5 rendering anomaly study. I am posting the issue publicly so other Unreal Engine developers can check whether it is reproducible, already known, or has a practical workaround.
I am seeing a repeatable temporal flicker in UE 5.5 when TAA and Screen Space GI are enabled together. The unstable region is not the entire frame; it is mainly the reflected/indirect light on glossy or mirror-like surfaces.
Repro setup:
- UE 5.5 on Windows.
- Deferred renderer.
- r.AntiAliasingMethod=2 for TAA.
- r.DynamicGlobalIlluminationMethod=2 for Screen Space GI.
- Slow camera translation or rotation while viewing a glossy surface receiving reflected/indirect light.
Observed result:
Bright reflected streaks or indirect-light patches appear, disappear, or jump between adjacent frames. I aligned adjacent frames from the capture, and the MSE spikes line up with the visible flicker.
Expected result:
The reflected/indirect light should change smoothly with the camera path, not drop out or jump from one frame to the next.
I also submitted this through the Unreal Engine Bug Submission Form and am using this thread to keep a public reproduction record.
Attachment note: I attempted to attach video_comparison.mp4 here, but this forum account is currently blocked by the forum’s new-user attachment restriction. The representative video was attached to the Unreal Engine Bug Submission Form submission and can be provided again when the forum allows attachments.