CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Hello,

It may not fit your need, but a simple solution is to use 
Delaunay_triangulation_3 and a vertex_with_info to compute the convex 
hull of your 3D points.

The customization of the vertex is described here:
http://www.cgal.org/Manual/last/doc_html/cgal_manual/Triangulation_3/Chapter_main.html#Subsection_35.6.2

to set the info you need to write something like:
  Vertex_handle v=t.insert(pt);
  v->info()=something;

then the vertices on the convex_hull can be retrieve using the vertices 
adjacent to the infinite vertex, like this:
  t.adjacent_vertices(t.infinite_vertex(), output_iterator);


If you really need to use the Convex_hull_3 package, then you will 
probably have to defined your own kernel as described here:
http://www.cgal.org/Manual/last/doc_html/cgal_manual/Kernel_23/Chapter_main.html#Section_9.5

S.


 wrote:
> Dear CGAL users,
> I want to attach an item per vertex to a set of points for which I want the
> convex hull (let say an index).
> I have understood that I need to refine CGAL::Polyhedron_items_3 as in the
> examples:
>
> examples/Polyhedron/polyhedron_prog_color.cpp
> examples/Surface_mesh_simplification/edge_collapse_enriched_polyhedron.cpp
>
> however in these examples, the custom field of the face/edge is filled after
> the construction, but I would like to provide a point with the appropriate
> index before a call to convex_hull_3.
> It probably means that I have to define my own kind of point (probably derived
> from one of the CGAL class).
> As I am not sure if this is even possible, I would be really happy if somebody
> can share her/his experience with such a problem such that I can switch to an
> other implementation as quickly as possible if my understanding is correct.
>
> Is there an example of such a specialization somewhere in the documentation
> that I missed?
> Did somebody already have solved this kind of problem?
>
>
> - thank you in advance,
>
> Manuel