Twisted Face problem in 2.40 Alpha2 but not in 2.37a ? BUG?


I’m having problems with creating faces in 2.40 Alpha2. I’m working with imported 2D DXF, vrml and .cob files converted from a cad package via a file converter app. These have no faces, I select 4 verts and hit F building up the 3D model as I go.

When i create faces from the verts and/or edges in 2.4 alpha 2, I’m getting a lot of what appear to be twisted faces, where in solid view they have a greyscale gradient appearance in perhaps one or two points on the face as if a couple of the verts are slightly lower or higher on the axis than the others making up the face. In the view properties dialogue all the vertices have the same vertical position on an axis accurate to 3 decimal places, it would appear.

Yet in 2.37a if I open the same blend files and pick the same verts in the same order as I did in 2.40 alpha2 and hit F there are no problems, no twisted faces. This problem makes 2.4 unusable to me for the models I’m working on. If i render the model it looks a mess of gradients not a smooth faces forming the model.

If i open a blend in 2.37a which was edited in 2.40 alpha2 and contains twisted faces, they appear in solid view as gradients, but when i click on the faces the greyscale gradient disappears and shows solid again.

If i then save that blend with no visible twisted faces and reopen it in 2.4 alpha 2 they’re back.

Can anybody explain what’s going on?


could it be to do with normals like on flipping faces. do vertices have normals?


Yes, Verts have normals, but you don’t have access to them except thru Python (and, of course, rotating them manually in edit mode).

What happens when you use “X-Sort” in Mesh Tools and/or Ctrl-F in Object mode?


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Thanks for your help. Neither xsort or ctrl F have any visible effect on the troublesome meshes.

It does look like a normals problem and it really looks like there are differences between the way 2.37a and any build after that handles the meshes I’m working with. This problem started when I began using CVS builds beyond 2.37a and continues to be a problem with 2.40 alpha2.

thanks again


Would you please send me the file? I’m interested to see it ([email protected])


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I think I’ve solved it. I searched on sorting normals and came across manifold and non manifold, inside faces / edges, also some python scripts for manifold and unusual manifold detection as blenders tool didn’t / doesn’t work correctly. Blenders script highlighted quite a few edges that needed flipping, the external python scripts didn’t detect any.???

So i did ctrl shift n to recalculate normals inside and it fixed the meshes.

Don’t know why there appears to be a difference in the way 2.37a and 2.40 alpha2 handle them by default, but sorted for me i think.

thanks again for your help and pointing me in the right direction.