CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Nicholas Mario Wardhana wrote:
> On 13 January 2011 15:01, Sebastien Loriot (GeometryFactory)
> <>
>  wrote:
> > I am quite surprised by your answer. What are the limitation of the
> > existing data structures?
>
> Hi Sebastien,
>
> What we abandon is the idea of using half-edge representation.
> Previously we were about to implement a method to compute the
> intersections of some polyhedra, which are represented by their
> half-edges. However, after our recent internal discussion, it turned
> out that our previous method was too complicated, so we are trying
> different approach. So far face-vertex (FV) representation is enough
> for this purpose, and we are not sure whether either CGAL or OpenMesh
> directly supports it. For CGAL, we can't find a class like polygon in
> 3D space to represent the face, and I suppose the face classes in both
> CGAL and OpenMesh (HalfedgeDS<Traits,Items,Alloc>::Face in CGAL and
> OpenMesh::PolyMeshT<Kernel> in OpenMesh, although I am not really sure
> about the latter) are quite closely related to half-edge structure
> (please correct me if I am wrong), so currently we develop our simple
> FV data structure.
>
> My apology if I did not make myself clearly enough in the previous
> e-mail, and thank you.
>
> Best regards,
> Nicholas Mario Wardhana
The Polyhedron_3 class of CGAL documented here:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Polyhedron_ref/Class_Polyhedron_3.html
provides iterator over vertices,facets and halfedges.

Given a facet, you can use Halfedge_around_facet_const_circulator to get 
the vertices of a face (using the incident vertex to each halfedge).

See: 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Polyhedron_ref/Class_Polyhedron_3-Traits---Facet.html

I don't want to prevent you from implementing your own data structure if
you think it will be more efficient but you may save time by using an
existing one (in particular because many additional functionalities are 
available in CGAL).


S.