Alpha Shape 3D

unhandled

(Laurent Delrieu) #1

Here is an implementation of 3D alpha shape, it is using 3D DelaunayCell (standard GH component ??).
https://doc.cgal.org/latest/Alpha_shapes_3/index.html
https://doc.cgal.org/latest/Alpha_shapes_2/index.html

I liked a lot the explanation of Alpha Shape of CGAL site “Imagine a huge mass of ice-cream making up the space R3R3 and containing the points as “hard” chocolate pieces. Using one of these sphere-formed ice-cream spoons, we carve out all parts of the ice-cream block we can reach without bumping into chocolate pieces, thereby even carving out holes in the inside
The little sphere gives the size of the “spoon”



The script has 2 flavors, one single CPU and one Multithreaded (2-4 times faster with 8 CPU)


Smothed outer surface from a 3D set of points
Volume from points in 3D Space (problem with invalid mesh)
(Michael Pryor) #2

Nice! 3D DelaunayCell is from mesh edit


(Laurent Delrieu) #3

There are some problems, my way of doing is not very good. I must see if output of 3D Delaunay Cell is ordered !
Meshes have duplicate faces. So at the moment I have no better solutions than removing them !! But there are other problems. It will take some times to solve.


(Michael Pryor) #4

Meshes have duplicate faces. So at the moment I have no better solutions than removing them

Try that

http://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_Geometry_Collections_MeshFaceList_ExtractDuplicateFaces.htm


(Laurent Delrieu) #5

Thanks Mickael,
but this command add holes in my mesh so I wrote mine command and add some others tests. It seems now that my script is more robust, except for little radius.


Alpha Shape 3D Legacy.gh (54.7 KB)


(Laurent Delrieu) #6

Carving Ice Cream :yum: I found the analogy very good.



(Michael Pryor) #7

You are not allowed to have so much fun here :smiley:
Really nice study!


(Laurent Delrieu) #8

Thanks,
It is fun yes and I wanted to go a bit deeper in Alpha Shape and trying to generate a Brep with “spoon” cutters. Depending on the shape there are some holes.
here a Wip Mesh cutter


mesh carving.gh (7.7 KB)