I'm trying to create a spherical object using a screw modifier on a mesh created using a mirror modifier.

The first screenshot shows my mesh created by applying a mirror modifier over the x axis.

Mesh created by applying mirror modifier on x axis

The second screenshot shows the screw modifier applied.

enter image description here

The problem is the split in how the upper and lower halves are shaded (darker on top). Is there a way to fix this?

  • 2
    $\begingroup$ Probably you should check the 'calc order' option in the screw modifier panel $\endgroup$ – lemon Mar 3 '17 at 16:28
  • $\begingroup$ This fixed it. Is there a setting on mesh that can be changed without having to do it on the modifier? Just trying to understand why this works / what it is actually fixing. $\endgroup$ – bingles Mar 3 '17 at 17:50
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    $\begingroup$ This is due to the mirror: mirrored, the edges are inverted. So when screwed, that creates faces with inverted normals. What you can do: screw the half first, then mirror after that. It does not guaranty back/front faces but all will be in the same orientation. But anyway, 'calc order' is here to handle the situation. $\endgroup$ – lemon Mar 3 '17 at 18:08

I think the issue may be that your normals are flipped: In 3d each face has a 'normal' that represents which way the lighting should be interpreted. To fix this, in edit mode press CTRL + N. This will try to flip the normals so they point outwards. If this does not fix it, open your toolshelf and look to the Operators menu at the base of it (Looks like this). Check the box saying 'Make normals consistent inside'.

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    $\begingroup$ This would help only if mesh was composed from faces, but there are none in the question (modifier's result is not counted as it doesn't exist yet). Vertices normals are the ones affecting this behaviour. $\endgroup$ – Mr Zak Jun 15 '17 at 12:44

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