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Questions on constructing graphical objects using relatively complex computations relating to the mathematical structures defining those objects. Examples include convex hulls, Voronoi diagrams, Delaunay triangulations, mathematical constructions, symmetries, genuses of curves and graphs and programmatic constructions of polyhedra.

22 votes
5 answers
5k views

Insphere for Irregular Tetrahedron

I am looking for existing Mathematica code to compute the unique sphere inscribed inside an irregular tetrahedron. I can write it myself, but I would love to find that someone already performed this c …
Joseph O'Rourke's user avatar
10 votes
2 answers
504 views

RegionIntersection puzzle

I am using RegionIntersection[] to intersect two rectangles, phrased as Polygon[]s: RegionIntersection[] returns an incorrect result (the green region above; detail below), and issues a series of e …
Joseph O'Rourke's user avatar
7 votes
3 answers
427 views

Can one use MeshRefinementFunction to obtain a nonobtuse triangulation?

I have a planar convex polygonal region Rc. I would like to triangulate it such that every triangle is nonobtuse. I was hoping that the MeshRefinementFunction option would indeed "refine the simplex" …
Joseph O'Rourke's user avatar
4 votes
2 answers
277 views

Clean & efficient bounding box non-intersection test

I would like a quick test to tell me that segments $ab$ and $cd$ cannot intersect in the plane. If the maximum $x$-coordinate of $a$ and $b$ is less than the minimum $x$-coordinate of $c$ and $d$, the …
Joseph O'Rourke's user avatar
5 votes
1 answer
287 views

Are the triangles in DelaunayMesh oriented ccw?

MeshCells[R, 2] returns the triangles from R=DelaunayMesh[pts], where pts is a list of 2D points. My (limited) experiments indicate the triangle vertices are listed in counterclockwise order, which is …
Joseph O'Rourke's user avatar
10 votes
3 answers
418 views

RegionMember[ ] in polygon

Bug introduced in 10.0 and fixed in 12.0. I am seeing a difference in RegionMember[ ] testing a point inside a 3-vertex polygon and testing a point inside a more complex polygon: poly1 = {{0, 0}, …
Joseph O'Rourke's user avatar
5 votes
1 answer
166 views

VoronoiMesh with boundary edges removed

I would like to create a Voronoi diagram without the boundary edges highlighted. This code gVD = VoronoiMesh[X, MeshCellStyle -> {{1, All} -> {Thick, Red}}] produces the 1st image [left/top] (X is my …
Joseph O'Rourke's user avatar