Any light's min roughness setting creates black artifacts with materials who have a roughness value less than 0. The min roughness must be =< 0.

Steps to Reproduce
  1. Open Blank Project
  2. Drag a basic sphere into the scene
  3. Open the material and set the roughness to any negative value.
  4. Open the directional light and set it to movable
  5. Set the min roughness value to 0

The sphere will display a large black area.

The sphere looks mostly similar aside from the glossy highlight.

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ComponentUE - Rendering
Affects Versions4.
Target Fix4.13
Fix Commit3076489
Main Commit3092051
CreatedAug 9, 2016
ResolvedAug 12, 2016
UpdatedMay 2, 2018