CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Note that the alpha shape has this constructor:

Alpha_shape_3<Dt> A ( Dt& dt, FT alpha = 0, Mode m = REGULARIZED);
        Build an alpha shape of mode m from the triangulation dt. Be
        careful that this operation destroy the triangulation.



You can first insert your points in the triangulation and then construct 
the alpha shape from the triangulation.

Note that the vertex type of the TDS should be:
CGAL::Alpha_shape_vertex_base_3<Traits,Vb> where Vb is the triangulation
with info vertex type.


See here how to insert points and info:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_3/Chapter_main.html#Subsection_38.5.3

Alpha_shape_3 reference page:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Alpha_shapes_3_ref/Class_Alpha_shape_3.html

Sebastien.

Farhad Bazyari wrote:
> Hello,
>
> Sorry this might be a very newbie question.
> I'm looking for a simple example that constructs an alpha_shape and assigns 
> user info (a pointer in this case) to each vertix.
> Something similar to example 38.5.2
>
> This arrangement doesn't compile:
>
> typedef CGAL::Exact_predicates_inexact_constructions_kernel Gt;
>
> typedef CGAL::Triangulation_vertex_base_with_info_3<CGAL::Color, Gt>          
> Vb;
> typedef CGAL::Alpha_shape_cell_base_3<Gt>            Fb;
> typedef CGAL::Triangulation_data_structure_3<Vb,Fb>  Tds;
> typedef CGAL::Delaunay_triangulation_3<Gt,Tds>       Triangulation_3;
> typedef CGAL::Alpha_shape_3<Triangulation_3>         Alpha_shape_3;
>
> typedef Gt::Point_3                                  Point;
> typedef Alpha_shape_3::Alpha_iterator               Alpha_iterator;
>
> Many thanks,
> Farhad
>
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