I was in the process of modelling a part, but then noticed that the faces were not being shaded properly (smooth shading with auto-smooth normals). Upon closer inspection, all face normals are in the correct direction but the vertex normals do not seem to be correct. Recalculating normals does not appear to fix the problem. How do I recalculate the vertex normals?

I am unsure of the modelling steps that lead to this shading issue and have not successfully replicated the issue.

I am aware that it would not take very long to remodel the part but am curious about this issue.

enter image description here enter image description here enter image description here

  • $\begingroup$ Yeah, that's weird. I played around for a bit, I can see the vertices that are giving split normals, but I can't find out why or fix it. There really doesn't seem to be any reason they should be like that. $\endgroup$ – Christopher Bennett Jul 22 '20 at 1:59
  • $\begingroup$ The issue appears to be linked to the object...if I add a circle into the existing object and remodel the part, I get the exact same normal issue. If I add a circle as a separate object and remodel the part, everything works fine. I suppose I'll put in a bug report about it. $\endgroup$ – stphnl329 Jul 22 '20 at 2:00
  • $\begingroup$ Yeah, I also tried deleting both the edge and face and then rebuilding, but the "seam" reappeared. Very odd. $\endgroup$ – Christopher Bennett Jul 22 '20 at 2:08
  • $\begingroup$ @ChristopherBennett found the issue, it was the scaling of the object. If you set the scale of the object back to 1:1:1, you'll notice that the source mesh is actually very flat with a sharp edge. Applying the scale fixes the issue. Credits to Rahul Chaudhary on developer.blender.org for the solution. $\endgroup$ – stphnl329 Jul 22 '20 at 4:16
  • $\begingroup$ Very interesting problem, this object had me perplexed for some time trying to figure it out, turns out it was as simple as applying the scale ! $\endgroup$ – Gorgious Jul 22 '20 at 7:53

Credits to Rahul Chaudhary on https://developer.blender.org/ for the solution.

Turns out the issue is a result of the abnormal scaling I had originally placed on the object to scale a cylinder down to the approximate diameter and height (.078 in XY, 4.888 in Z). Applying the scale immediately fixed the issue.

To clarify, this would be the mesh Blender used to calculate all of the normals, after which it rescaled the mesh to look like the cylinder I had. enter image description here

Before Applying Scale: enter image description here After Applying Scale: enter image description here


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