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157

answers:

2

I'm using Delaunay to triangulate a concave polygon, but it fills in the concavities. How do I automatically remove the triangles that are outside the polygon boundaries?

A: 

You shouldn't, you should find a Delauney routine that handles boundaries correctly.

Alternately you could, assuming you know the edges, go through every triangle and delete those that cross an edge. Search for segment-segment interestion tests for code to do this.

Martin Beckett
A: 

Self-answer: in some cases, this is impossible. I needed to use a constrained Delaunay algorithm: http://www.cs.cmu.edu/~quake/triangle.delaunay.html

Archagon