CGAL users discussion list

[Manuel Yguel <>]

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?

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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