Anisotropic rotation on Principled BSDF

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Brandroid
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Joined: Thu Feb 23, 2017 8:48 pm

Anisotropic rotation on Principled BSDF

Post by Brandroid » Thu Aug 10, 2017 7:29 pm

I only recently realized this, so I thought I'd share just in case anyone else runs into it. A lot of my early Cycles 4D shaders relied on PBR techniques using the Anisotropic shader for metals. After modifying some of these older shaders over to the new Principled BSDF, I realized that the anisotropy occurs at a 90° angle to the older shader. When using the UV map to drive the tangent input on a shader, you'll need to take this into account.

Luckily there's an easy fix. If you don't want to modify your UV coordinates, simply use .25 in your Anisotropic Rotation value on the shader. This is equivalent to rotating the UVs 90°.

Old network and result:
CINEMA 4D_2017-08-10_15-16-50.jpg
CINEMA 4D_2017-08-10_15-16-50.jpg (64.44 KiB) Viewed 529 times
anisotropic-shader.jpg
anisotropic-shader.jpg (230.67 KiB) Viewed 529 times
New network and undesired result:
CINEMA 4D_2017-08-10_15-13-40.jpg
CINEMA 4D_2017-08-10_15-13-40.jpg (36.83 KiB) Viewed 529 times
principled-anisotropy.jpg
principled-anisotropy.jpg (156 KiB) Viewed 529 times
After rotation value of .25:
principled-anisotropy-rotated.jpg
principled-anisotropy-rotated.jpg (198.77 KiB) Viewed 529 times

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