Assuming I have a model with several n-gonal faces, out of which some might not be convex polygons, what can I do to make blender split those that are concave to make sure all polygons are convex?

I know about the "Triangulate" tool, but is there something that only splits the faces if they're convex?


Added screenshot clarifying what I need:Blender screenshot showing some convex polygons that do not need triangulation, and concave ones who do need it.

So again: I need a tool that lets me select it all, and then subdivides the concave polugons into only convex ones.

  • $\begingroup$ Have you tried the decimate modifier or the triangulate modifier? Modifiers might be your answer. $\endgroup$ Jan 30, 2015 at 16:36
  • $\begingroup$ Well they both kind of don't do what I'm asking about. Decimate actually reduces the amount of polygons! What I need is like triangulate, but only to be applied to concave triangles. $\endgroup$
    – Ludwik
    Jan 30, 2015 at 17:51
  • $\begingroup$ What I was thinking was adding a subsurf modifier then decimating it to get the original poly count. Depending on the kind of model. Could you post a screenshot of the model so I could think so more on it? $\endgroup$ Jan 30, 2015 at 20:38
  • $\begingroup$ This isn't for one specific model, rather, I'm planning a project and I'll need the thing that I'm asking for in it. But it's 2D level design, so: very basic surfaces, actually not even bending into the third dimension, no curves etc... Should only be a collection of polygonal faces, with different properties. I can add a screenshot of an example, hold on a sec... $\endgroup$
    – Ludwik
    Jan 30, 2015 at 23:17

2 Answers 2


Blender 2.75 now has a feature a tool to perform exactly this operation.

Mesh > Cleanup > Split Concave Faces

Example splitting ngons


You could use Select > Select Faces By Side, set Number of Vertices to 4 and change type to Greater Than. This will select all ngons, from there you can safely triangulate. As an added bonus, if the ngon has a large number of even sides, you could even run a tris to quads operation after if you want to have that clean flat topology.

  • $\begingroup$ This is better than simple triangulation, because the tris-to-quads step won't create concave quads, as I feared. However, this method still won't allow convex >4 vertice polygons to stay. In your gif, there would be nothing that needs doing, by my requirements. All polygons are already convex, and in the end result, the big hexagon is unnecessarily split. Any method that avoids that, but still splits concave polygons into convex ones? $\endgroup$
    – Ludwik
    Jan 31, 2015 at 21:34
  • $\begingroup$ @Ludwik Did you try any of the commands outside of looking at my example and afraid not, they are simple tools. Also could use limited dissolve to get a concave quad from a triangulated shape. $\endgroup$
    – iKlsR
    Feb 1, 2015 at 1:06

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