I have a set of points that form a concave polygon. I've performed a Delaunay triangulation on them that gives me this: Delaunay. I then used the descartes.PolygonPatch function to give me the concave polygon I want: Polygon. Now I want to recover only the points that were used in this patch, and sort them in order. Any suggestions on how I can do this?
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Can you provide sample code and data? – tfv Apr 15 '16 at 14:56
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I'm trying to follow what HumanGeo did here: http://blog.thehumangeo.com/2014/05/12/drawing-boundaries-in-python/ , except that instead of the patch, I need the (ordered) vertices on the boundaries of the patch. – phalanx Apr 15 '16 at 15:22
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Looks like the alpha shape of a set of points. http://doc.cgal.org/latest/Alpha_shapes_2/index.html. If you have delaunay triangulation in a datastructure such as half-edge, quad-edge etc., finding the alpha shape is fairly straight forward (http://people.mpi-inf.mpg.de/~jgiesen/tch/sem06/Celikik.pdf). Although, if you choose to use any algorithm, that does not let you keep the topological connectivity information from the triangulation, the only option pretty much is basic brute force search. Quadtrees or morton-codes might make life easier. – hkrish Apr 18 '16 at 15:02