CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

As documented here:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/TriangulationDS_3_ref/Concept_TriangulationDataStructure_3.html 
a Facet is a pair (Cell_handle,int). The integer indicate the index of 
the cell opposite to the facet. So getting access to the points of the 
facet can be done like this: it->first->vertex( (it->second+k)%4 
)->point() with k=1->3.

Note that if you are interested in a triangulation of a sphere (i.e. a 
surface triangulation), you need to consider only facets incident to an 
infinite cell.
Also, using the convex-hull solves this problem, see this example
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Convex_hull_3/Chapter_main.html#Subsection_16.2.3.

Sebastien.


horstmann wrote:
> Hi there, I'm new with CGAL, i'm sure my question is very simple. 
>
> I am trying to use CGAL to do some Delaunay triangulation. I have a grid
> with N 3D points over a sphere and I want to triangulate the sphere using
> those points as the vertex of the triangles. I just need to get a list of
> the vertex of the resulting triangles like that: 
>
> id_triangle1 vertex_1 vertex_2 vertex_3 
> id_triangle2 vertex_1 vertex_2 vertex_3 
> ....... 
>
> I have done that to perform the triangulation: 
>
>
>         std::vector<Point> P; 
>         for(i=0;i<NSPOINTS;i++) 
>                 P.push_back(Point(GRID[i].x,GRID[i].y,GRID[i].z)); 
>
>         // building Delaunay triangulation. 
>         Delaunay dt(P.begin(), P.end()); 
>
>
> The problem I have is that I have no idea how to get the resulting
> triangulation. I figured out how to get the face_iterator, but I don't know
> what to do from there: 
>
>
>         Delaunay::Finite_faces_iterator it; 
>         for (it = dt.finite_faces_begin(); it != dt.finite_faces_end();
> it++){ 
>                 std::cout << dt.triangle(it) << std::endl; 
>         } 
>
> I'm not sure if that is correct to iterate over the triangles, and if it
> is... 
> a triangle = face ??¿ , i mean , each iterator position have only a
> triangle¿? 
> How can I get correctly the x,y and z of each triangle¿?¿ 
>
> Thank you a lot in advance! 
>
> --
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