When "r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat=1", some values for the Sky Atmosphere at some directional light angles can lead to the sun disk being cut off, and taking on a chord shape.
Also tested on //UE5/Release_5.6, CL: 45232827
1. Download the attached test project and open
2. Face where you can see the sun disk
3. Toggle the value of the CVar "r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat" between 0 and 1
3. Observe when this CVar is enabled, the sun is cut off half way.
4. With the CVar on, slightly rotate the directional light (recommended to have snapping off)
5. Observe the cutoff point is global, rather than relative to the sun disk.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-372110 in the post.
| 0 |
| Component | UE - Rendering - Graphics Features |
|---|---|
| Affects Versions | 5.6, 5.7.4 |
| Fix Commit | 52376877 |
|---|
| Created | Mar 30, 2026 |
|---|---|
| Resolved | Apr 2, 2026 |
| Updated | May 1, 2026 |