CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

On jeudi 05 mai 2011 19:06:47 Bruce Duncan wrote:
> Let me know if images or code would help clarify what I'm trying to do.

Yes, sure! Your message is rather imprecise.

> Hi all,
> 
> I am writing a mesh generator with quite specific requirements. As a
> result, I need to output a polyhedron in CGNS format.
> 
> I can do the CGNS output very easily if I have a set of tetrahedra. In fact
> I have already implemented this to output a Triangulation_3.
> 
> At first I tried to use Triangulation_3 and it's siblings directly.
> However, they don't take into account edges and my concave polyhedra are
> destroyed in the process of triangulation. Is there a way around this?

What have you tried exactly? How did you "use Triangulation_3"?

> Next, I turned to the Mesh_triangulation_3 class. This accepts a Polyhedron
> and gives access to a Triangulation_3. Excellent! The problem is that it
> does not respect the vertices and edges of the input Polyhedron. My
> application really depends on having the vertices remain in the same
> place. Other vertices and edges may be added, however. Is there a way to
> achieve this?

The class Mesh_triangulation_3<Polyhedron>::type in itself is just a regular 
triangulation with speciall vertex and cell types.

Let's assume you have used the function CGAL::make_mesh_3 or 
CGAL::refine_mesh_3 to construct a 3D mesh from your polyhedron.

> I have tried to use the Polyhedral_mesh_domain_with_features_3 class but
> without much success... I may post a test case about that next week.

The 3D mesh generator, in CGAL, with features or not, will remesh the 
polyhedral domain. If there are features, for examples sharp edges to 
respect, 
then those features will remeshed. You cannot use the CGAL 3D mesh generator 
in a way to respect the full set of vertices, edges, and facets of the input 
polyhedron.

If you explain better what you want to achieve, maybe we could suggest you 
other ways to do. What is that mesh generator you want to write? What are its 
requirements?

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/