CGAL users discussion list

[Dimitris Tzionas <>]

Hi all,

In a physics simulation I have a problem with concave meshes, so it seems that I really have to do decomposition in convex mesh-parts.

Since CGAL covered successfully past needs, I was hoping to use this again.

It seems that it is doable only by using Nef_polyhedron_3.

http://doc.cgal.org/latest/Convex_decomposition_3/index.html

In order to have this representation:

- I first read a .off file (ideally this should happen from memory, but my code is slower than CGAL's built-in reader from file) in a Polyhedron_3. My mesh is closed and depicted fine with the Polyhedron viewer demo.

- then I convert to a Nef_polyhedron_3.

- Finally I try to use CGAL::convex_decomposition_3

- The first part is very fast. 

std::ifstream file("/home/dimitris/Model_Hand_R.off");

file >> POL;

However instead of 10002 vertices I noticed that I get 

POL.size_of_vertices = 20004

POL.is_closed = 1

- The second part takes ~15sec for 20k vertices.

Nef_polyhedron_3 NEF( POL );

NEF.is_empty: 0

Nef vertices: 20004

Nef edges: 60000

Nef facets: 40000

Nef volumes: 3

- The third part takes forever and never returns anything.

CGAL::convex_decomposition_3( NEF );

Could it be that I'm doing something very obviously wrong?

Could I get best practices hints for this problem?

What is a sensible run-time for CGAL's approach?

Some extra info on the current setup:

typedef CGAL::Exact_predicates_exact_constructions_kernel       Kernel;

typedef CGAL::Polyhedron_3<Kernel>                              Polyhedron;

typedef CGAL::Nef_polyhedron_3<Kernel, CGAL::SNC_indexed_items> Nef_polyhedron_3;

Thank you in advance for potential hints,

Dimitris