Sequencer thumbnail renderer disables EyeAdaptation after explicitly enabling it, producing white thumbnails in bright scenes

General Issues and Bug Reporting (Unreal Engine)
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Summary

Sequencer Camera Cuts previews and automatic Level Sequence asset thumbnails can render completely white in physically bright scenes, even though the same CineCameraActor is correctly exposed in the editor viewport.

In TrackThumbnailUtils.cpp, Normal/Best thumbnail rendering explicitly enables EyeAdaptation and allocates a persistent ViewState. Later in the same function, an unconditional call to DisableAdvancedFeatures() disables EyeAdaptation again before rendering.

What Type of Bug are you experiencing?

Editor

Steps to Reproduce

  1. Create a level with a Directional Light set to approximately 60,000 lux.
  2. Add an unbound Post Process Volume using automatic exposure. For example, use Min EV100 = -10 and Max EV100 = 11.
  3. Add a standard CineCameraActor and verify that its view is correctly exposed in the editor viewport.
  4. Create a Level Sequence and add the CineCameraActor.
  5. Bind the camera to a Camera Cuts track.
  6. Set the Camera Cuts thumbnail quality to Normal or Best.
  7. Refresh the Camera Cuts thumbnails.
  8. Save the Level Sequence so its automatic asset thumbnail is generated.

Expected Result

The Camera Cuts previews and automatic Level Sequence asset thumbnail should have a reasonable exposure matching the CineCameraActor view. They should use the eye-adaptation state explicitly prepared by the thumbnail renderer.

Observed Result

The Camera Cuts previews and automatic Level Sequence asset thumbnail can render completely white, while the same camera remains correctly exposed in the editor viewport.

Reducing or replacing the bright Directional Light can hide the problem.

Affects Versions

5.8
5.7

Platform(s)

Windows

Additional Notes

For Normal and Best quality, TrackThumbnailUtils.cpp:

  1. Sets ViewFamily.EngineShowFlags.EyeAdaptation = true.
  2. Allocates a persistent ViewState.
  3. Sets ViewInitOptions.bInCameraCut = true so the target exposure is used without blending.
  4. Later calls ViewFamily.EngineShowFlags.DisableAdvancedFeatures(), which sets EyeAdaptation back to false.

A project-side Scene View Extension that restores only EyeAdaptation after DisableAdvancedFeatures() fixes both affected thumbnail types.
The issue reproduces with a standard CineCameraActor and is not specific to a custom camera rig.