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 repeated temporal artifact in UE 5.5 when thin bars/fences appear in reflection paths. The issue shows up as secondary reflection flicker, fence artifacts in mirror reflections, and sometimes inconsistent reflected visibility.
Repro setup:
- UE 5.5 on Windows.
- A scene with thin vertical bars, fence geometry, or narrow mirror strips.
- The thin geometry is visible directly and/or through a reflective surface.
- TAA/TSR enabled, with the exact reflection settings from conditions.json.
- Slow camera translation.
Observed result:
Thin reflected structures flicker, produce stripe-like artifacts, or appear to change occlusion/visibility across adjacent frames. The camera path is smooth, but the reflected thin geometry is not stable.
Expected result:
Thin geometry in the reflection path should remain temporally stable and should not change visibility abruptly during slow camera movement.
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.