CGAL users discussion list

[Manuel Yguel <>]

Thanks a lot.

Manuel

On Mon, Feb 15, 2010 at 3:38 PM, Sebastien Loriot (GeometryFactory)
<>
 wrote:
> 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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>>>
>>
>
>
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