Principled BSDF Anisotropy black faces
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Description

System Information
Win10, 1080Ti

Blender Version
Broken: 2.79

Short description of error
It seems that using anisotropy produces black odd artifacts under certain mesh circumstances. I don't think this happens often as it seems the actual mesh caused it, possibly by being a little bit too symmetrical?

I suppose often it goes unnoticed so I thought it might be good for someone to investigate upon if there isn't some inconsistency.

Rotating the object by the tiniest bit helps (probably helps by something being non 0 ^__^).

Moving random vertices randomly produces different results that are often completely correct or at least 50% correct. Good to try that in Rendered mode.

Screenshot:

Blend:

Details

Type
Bug

Would only know (other) workarounds:

  • move texture space slightly
  • actually use UVs (instead of radial) with a tangent node plugged into the tangent socket of the pricipled bsdf (meshes in you file already have UVs)

not even sure if this would be considered a bug (I can imagine tangent calculation being problematic in certain scenarios -- but could wrap my head around why this kicks in very specific cases)
been scratching my head for too long, better pass this on to @Brecht Van Lommel (brecht)

Bastien Montagne (mont29) triaged this task as Normal priority.Jul 22 2018, 5:38 PM