Description

Lumen generates a gradated shading even if objects are lit by a 360-degree constant sky light.
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I looked into this and found that this comes from Spherical Harmonics integration. Changing r.Lumen.ScreenProbeGather.DiffuseIntegralMethod from Spherical Harmonics to importance sample BRDF to game developers fix the dark shading.

I guess it's due to fast approximation with SH and it shouldn't be a big issue in most cases. But a licensee asked us to fix it so I'd like to make this jira for the issue.

Steps to Reproduce
  1. Open the attached project
  2. You can see gradated shading on a sphere
  3. Change r.Lumen.ScreenProbeGather.DiffuseIntegralMethod from Spherical Harmonics to importance sample BRDF
  4. The change made the shading completely flat.

Have Comments or More Details?

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-160191 in the post.

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Unresolved
ComponentUE - Rendering - Lumen
Affects Versions5.05.0.2
Target Fix5.2
CreatedJul 22, 2022
UpdatedSep 2, 2022