CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 05/08/2012 02:55 PM, horstmann wrote:
> Hi everyone,
>
> I'm almost new to CGAL and I have a Dealunay 3 Triangulation as in the
> example: "39.5.5   Fast Point Location for Delaunay Triangulations" in the
> following link:
>
> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3/Chapter_main.html
> CGAL Triangulation_3 Documentation .
>
>      typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
>      typedef CGAL::Delaunay_triangulation_3<K, CGAL::Fast_location>  Delaunay;
>      typedef Delaunay::Point Point;
>
>      std::vector<Point>  P;
>      // Insert some points.....
>
>      Delaunay dt(P.begin(), P.end());
>
> Then, I perform its convex_hull:
>
>      // define polyhedron to hold convex hull
>      CGAL::Polyhedron_3<K>  poly;
>
>      // Get only the surface
>      convex_hull_3_to_polyhedron_3(dt,poly);
>
>
> Once I have the triangulation and its conex_hull performed in dt and poly, I
> need to get the following info:
>
> - number of tetrahedron in the triangulation. (Is that just the number of
> cells?¿)
t.number_of_finite_cells() [1]

> - for each tetrahedron, the position of its four vertices (in ascending
> order).

Triangulation::Cell_handle cell=....
cell->vertex(i).point(); //for i=0; i<4
cf [2,3]

> - for each tetrahedron on the convex hull, the index (local index, i.e. in
> 1-4) of the vertex NOT on the convex hull
Iterate over infinite cells
(use the range all_cells_begin(),all_cell_end() and the 
is_infinite(Cell_handle) function documented in [1])
For each such cell, get the index of the infinite vertex,
using int i=cell->index(t.infinite_vertex()). Then use
Facet f=t.mirror_facet( Facet_3(cell,i) );
where Facet is
"typedef std::pair<Cell_handle, int>  Facet;
 (c,i) is the facet of c opposite to the vertex of index i"
as documented in [2]

Sebastien.

[1] 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3_ref/Class_Triangulation_3.html
[2] 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/TriangulationDS_3_ref/Concept_TriangulationDataStructure_3--Cell.html
[3] 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/TriangulationDS_3_ref/Concept_TriangulationDataStructure_3--Vertex.html


> Could anyone lend me a hand with that?¿?
> Thank you so much in advance!!
>
>
>
> --
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