I am trying to create a specific shape consisting of two curves connected together by faces (in the context of modelling a plane).

Here is what I came up with by converting the first curve to a mesh, extruding to get the second curve and applying some transforms (rotating and scaling). Screenshot

The problem I have is that because the scaling is not uniform on all the axes I get non-planar quads which get triangulated by Cycles: Render

I thought of different ways of fixing this:

  • Creating and converting the two curves separately gives a similar result
  • Dividing the quads by adding intermediate curves makes the quads flatter but it is not perfect

I know that it is mathematically possible, for instance if the algorithm converting a curve to a mesh divided the curve into segments according only to the angle and not the distance between vertices, so that's why I'm asking: does anyone know how to do this "the right way"? Thanks!

  • 2
    $\begingroup$ Having long faces like those is not recommended because it's easier to run into non planar geometry. Make subdivisions on them to accommodate for the curvature. Loop cuts (Ctr+R) would be one of the possible tools for this job $\endgroup$
    – user1853
    Sep 20, 2017 at 21:35
  • $\begingroup$ @cegaton Yes that's what my second bullet point refers to, this is the best I could do so far. But I know that in this particular case there exists a perfect solution (mathematically) and I wanted to know if there was a way to obtain it :-) $\endgroup$ Sep 20, 2017 at 21:37
  • 1
    $\begingroup$ Virtually all quads are non planar, and that is ok, that is not a problem per-se. Your topology seems correct, your problem lies in the generated triangulation and the fact that your faces are not shaded smooth. $\endgroup$ Sep 20, 2017 at 21:59
  • $\begingroup$ Add some loop cuts to shorten the length of the faces. As well as shade smooth, the subdiv modifier can help smooth the surface. $\endgroup$
    – sambler
    Sep 21, 2017 at 4:08

1 Answer 1


I tried to re-create your model to mimic the issue and as others stated in comments, adding some loop cuts should solve it.

enter image description here

After that I would just try to make the cuts more even using vertex slide.


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