CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

There is nothing specifically done for this.
By default, the vertices of a polyhedron are stored in a list so
direct access is not possible (except if the id is the iterator).

You can change the storage to use a vector instead of a list
(see
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/HalfedgeDS/Chapter_main.html#Subsection_26.3.3 

for how to  do it on the underlying HDS).
The drawback is that before inserting vertices in your polyhedron, you 
need to know an upper bound on the number of vertices (to avoid resizing
the vector). Once done, if your id is the order of insertion, you can
then use boost::next(P.vertices_begin(),id) to get direct access to the
vertex.

Sebastien.

On 08/29/2011 08:09 PM, Yifei Li wrote:
> Hi all,
>
> Given a polyhedron, how do you access a point by its id? I did not find
> any API in the documentation.
>
>   My polyhedron is declared as follows:
>
> template <class Refs, class P>
> struct MyVertex : public CGAL::HalfedgeDS_vertex_max_base_with_id<Refs,
> P, unsigned int> {
> ...
> };
>
> struct MyItems : public CGAL::Polyhedron_items_with_id_3 {
> ...
> };
>
> typedef CGAL::Polyhedron_3<Kernel, MyItems> Polyhedron
>
> Thanks
>
> Yifei