CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

What about adding an info in the vertex type?

See this example:
http://doc.cgal.org/latest/Triangulation_2/index.html#title40
using this class:
http://doc.cgal.org/latest/Triangulation_2/classCGAL_1_1Triangulation__vertex__base__with__info__2.html

Sebastien.

On 07/24/2015 05:40 PM, Daniel Duque wrote:
> Hello everyone.
>
> I have been using alpha shapes to identify the outer vertices of
> triangulations
> for some time, and I am very happy with the method. However, the
> underlying triangulation
> is destroyed in the process. This often OK, but can be inconvenient if
> one just wants to "mark"
> the nodes as outer, but keeping the triangulation. Right now I am doing
> this crude treatment
> which, as you see, copies the triangulation, destroys it, then marks the
> vertices on the original
> triangulation as outer if the coincide with the nodes of the alpha shape.
>
> The crudest part, as you can see, is that this coincidence is
> implemented by "locate", since
> I have lost any other connection with the original triangulation. I
> guess I could hack the
> copy procedure in order to include a pointer or handle to the original
> one...
>
> Any ideas will be welcome.
>
> Best,
>
> Daniel Duque
> UPM
>
> // T is a global Delaunay triangulation
>
> void surf_detect(void) {
>
>    Triangulation T2(T);
>
>    FT hh= 1.2 * simu.h();
>
>    FT alpha=hh*hh;
>    Alpha_shape_2 al( T2, alpha );
>
>    for (Alpha_shape_vertices_iterator asv=al.alpha_shape_vertices_begin();
>         asv!=al.alpha_shape_vertices_end();
>         ++asv) {
>
>      Point p=(*asv)->point();
>
> //  mark vertices in the alpha shape as boundary vertices
> //  implemented by locate (not very efficient, I guess)
>
>      int i;
>      Triangulation::Locate_type lt;
>      Face_handle fc=T.locate(p, lt , i );
>      fc->vertex(i)->boundary.set( true );
>    }
>
>    return;
> }