CGAL users discussion list

[Mengda Wu <>]

You mentioned CGAL surface mesher can directly generate triangle with size adapted to the curvature.
But how to do it? Currently I am only able to generate isotropic triangles.

Thanks,
Mengda

On Fri, Jul 17, 2009 at 2:43 AM, Andreas Fabri <> wrote:

Hi Christian,

You might further investigate the surface mesher, as comparing it with
a marching cubes algorithm is comparing apples and pears. The surface
mesher will produce quality triangles, and you can have uniform sized
triangles or triangles with the size adapted to the curvature, that
is few triangles where the surface is flat, and many triangles where
you have high curvature.   So in order to have a fair comparison,
you should compare it to marching cubes followed by mesh simplification.

Obvioulsly if badly shaped triangles are not a problem for your use case,
the added value I try to point out, is not valuable for you.

Best regards,

andreas

Christian Walder wrote:

I see, thanks. Can anyone recommend a good c++ implementation of the marching cubes algorithm? I am quite surprised that this is not easier to find...

On Fri, Jul 17, 2009 at 11:09 AM, Mariette Yvinec < <mailto:>> wrote:

   CGAL Surface mesher is not a marching cube.
   It builds  iteratively a sampling adapted to the surface geometry
   so that the restricted triangulation  of this sampling is
   an accurate approximation of the surface and a nice
   surface mesh formed with well shaped triangles.


   Christian Walder wrote:

       Dear All,

       I have used the CGAL library to perform marching cubes on an
       implicit surface. Unfortunately it is extremely slow -
       previously I have used a different implementation from an
       unknown author, and it is orders of magnitude faster for roughly
       the same resolution. I am wondering if I have called the
       functions correctly, and whether there are any easy ways attempt
       to speed it up.

       Best Regards,

       Christian

       ps.

       The key snippet of code is the following:

        Tr tr;            // 3D-Delaunay triangulation                                                                   C2t3 c2t3 (tr);   //
       2D-complex in 3D-Delaunay triangulation                                                     Surface_3 surface(implicit_function,
       Sphere_3(Point_3(center[0],center[1],center[2]), radius));
        // defining meshing criteria                                                                                           CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,  //
       angular bound                                                                                          radius_bound,  // radius bound                                                                                        distance_bound); // distance bound                           CGAL::make_surface_mesh(c2t3, surface, criteria,
       CGAL::Non_manifold_tag());
       

   --    Mariette Yvinec
   Geometrica project team
   INRIA  Sophia-Antipolis  

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