Wish: Concave Hull

Concave hull is a very common problem.
I use the VB script from here:
https://www.grasshopper3d.com/forum/topics/connecting-points-in-sequence

It would be nice to have it in GH2.

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it is a very good idea, there are many methods
http://www.portailsig.org/content/sur-la-creation-des-enveloppes-concaves-concave-hull-et-les-divers-moyens-d-y-parvenir-forme

Alpha Shape


K-nearest
https://www.researchgate.net/publication/220868874_Concave_hull_A_k-nearest_neighbours_approach_for_the_computation_of_the_region_occupied_by_a_set_of_points
Alpha Concave Hull
https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwiZxPOTyIfcAhXIShQKHRLpDrAQFgg4MAE&url=https%3A%2F%2Farxiv.org%2Fpdf%2F1309.7829&usg=AOvVaw3niXMWUfjpss7elOCUMHzc
Delaunay method
Suppress too big triangles

Here a script that shows differents implementations of Concave Hull



You need Alpha Shape, Clipper…
Concave Hull Methods.gh (50.0 KB)

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David’s method delivers different results for very similar cases.
As for those profiles in the image: the middle one will always come out wrong even thought I slide the F input between different values. Sometimes I get a self-intersecting curve.

Thanks for putting these algorithms together laurent - extremely helpful reference.

Fantastic!

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