I created a model in another program, and imported it to Blender to map the UVs. Parts of the model are symmetrically flipped mesh planes. I noticed in Blender that the mirrored objects display as darker, and on further checking, I find that the face and vertex normals are in one direction and the "vertex-per-face" normals are opposite.

I've tried the Recalculate Outside and Flip Normals commands, but that just inverts them without unifying the direction. How can I flip JUST the "vertex-per-face" to get them all in the same direction, as they are in the original un-mirrored object that was copied?

Weird Normals

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    $\begingroup$ Most likely that's because of custom split normals imported with the object from the 3rd party software; most likely you'll need to remove it in the Object Data tab > Geometry Data rollout. You'll reconstruct shading in Blender if you need it. $\endgroup$ – Mr Zak Apr 19 '17 at 23:10

Those purple lines are normals generated by Auto Smooth. It has checkbox under the Object Data tab > Normals rollout. I would recomend you just turn that feature off. If you want some complex shading, you should generaly use Sharp Edges with an Edge Split Modifier.

enter image description here

| improve this answer | |
  • $\begingroup$ There always will be normal vectors generated when adjusting edge split because of splitting, no matter which way to use - Autosmooth or Edge Split. As of several recent Blender versions Autosmooth has support of sharp edges, so it's essentially the same as modifier (the only difference is normals exporting) $\endgroup$ – Mr Zak Apr 19 '17 at 23:07

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