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I can not figure it out which triangulation algorithm is used to create these triangles in the attached picture. I think it is not delanuay or ear clipping but which polygon triangulation method create these triangles? Any help? picture of triangulation

weston
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user51044
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  • The algorithm appears to be drawing a line from every corner of the shape to every other corner of the shape possible. But it seems to be not drawing lines if the line would cross over other existing lines. – Noam Hacker May 05 '16 at 18:30
  • It seems Iike ear clipping. In any case it is polygon triangulation. – Ante May 05 '16 at 21:02
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    Why do you exclude ear clipping ? –  May 06 '16 at 07:20
  • Definitely not Delaunay, because no sphere circumscribing a tetrahedron in the triangulation can contain any other point https://cnx.org/contents/WSTSJiRY@10/Molecular-Shapes-and-Surfaces#DelaunayTriangulation – weston May 06 '16 at 13:57
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    @weston: this would be constrained Delauney, so the circumcircle rule doesn't hold. –  May 06 '16 at 13:58
  • @YvesDaoust ah thanks – weston May 06 '16 at 14:01
  • I exclude ear clipping because I tried same polygon and two triangles vere different from ear clipping as you can see in the my answer – user51044 May 06 '16 at 16:18
  • but it can be another version of an ear clipping method. Do you have any suggestions? It is extremetly important for me to figure out the algorithm – user51044 May 06 '16 at 17:12
  • Couldn't it be ear clipping, but turning the other way round as compared to the one you showed in the comparison image ? – BrunoLevy May 06 '16 at 19:57
  • Any triangulation of a polygon can be obtained by ear clipping. – weasel - Peter Palfrader May 07 '16 at 07:38
  • Recall that a Delauney triangulation maximizes smallest angles. Many of these polygon triangulations could be improved (wrt that metric) by flipping a few spokes. Thus these are not Delauney triangulations. – weasel - Peter Palfrader May 07 '16 at 07:40

3 Answers3

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I don't think it is ear clipping because you can see the difference in the attached example. But they are almost same except two triangles.

Difference between ear clipping and triangulation:

enter image description here

StayOnTarget
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user51044
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You need to use Triangle.Net open source library. It features many options including the ability to enrich contour points to maintain a specified triangle aspect ratio.

abenci
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It looks like it decomposes the concave polygon into a union of convex polygons, then creates a triangle fan for each of the convex polygons. But it's difficult to be certain.

Thomas
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