CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Manuel Yguel wrote:
> Thanks a lot for the quick answer.
> Unfortunately I need a convex hull because I need to find a Delaunay
> triangulation of points onto a sphere.
>
> However I just read a post by Monique Teillaud about spherical
> Delaunay triangulations: do you know if it is already possible to use
> the spherical kernel to compute Delaunay triangulations?
Not yet but as written in this tech report and as I said you can use the 
Delaunay Triangulation 3 for this purpose.
If you need triangles, you can use the method:
  t.incident_cells ( t.infinite_vertex(), output_iterator)



> I will write my own kernel (thanks for the link, I would not have had
> a look so deep in CGAL without it) and it would be a good exercise to
> improve my CGAL capabilities.
>
>
> - best regards,
>
> Manuel
>
>
>
>
>
> On Mon, Feb 15, 2010 at 3:06 PM, Sebastien Loriot (GeometryFactory)
> <>
>  wrote:
> > 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
> >
> > --
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