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Autosmooth with zero degree angle is different from plain flat shading
Closed, ArchivedPublic

Description

System Information
Win7 64bit

Blender Version
Broken: 2.78c

Short description of error
Smooth mesh with zero angle autosmooth is different from plain flat.

Exact steps for others to reproduce the error
Left mesh is plain flat, right - smooth&autosmooth


Details

Type
Bug

Event Timeline

Sergey Sharybin (sergey) triaged this task as Confirmed, Medium priority.

@Bastien Montagne (mont29), afraid another one for you. Seems Subsurf modifier has something to do here (removing it makes shading the same, but applying it doesn't solve issue). Maybe something related to world coordinate as well..

Bastien Montagne (mont29) closed this task as Archived.Aug 14 2017, 4:03 PM

Thanks for the report, but this is not actually an autosmooth/custom normals issue, but rather a Blender Internal engine issue, which has different codepaths for faces tagged as flat, and those tagged as smooth. You can check it by using Cycles - there results are exactly the same whichever option you use.

Not sure why BI has different behaviors (could also be a mere precision issue, maybe…), but don’t think it's worth spending time on this now, BI is doomed to be removed in Blender2.8 anyway.