CGAL users discussion list

[Nico Kruithof <>]

Hi,

I don't know too much about the mesh simplification algorithm, so I
can't help you there. From the skin surface point of view, I would
suggest to put 
---
Union_of_balls_3 union_of_balls(ball_set.begin(), ball_set.end(),
Traits(), true);
CGAL::mesh_union_of_balls_3(union_of_balls, p);
---
in a block:
---
{
  Union_of_balls_3 union_of_balls(ball_set.begin(), ball_set.end(),
Traits(), true);
  CGAL::mesh_union_of_balls_3(union_of_balls, p);
}
---
This because the Union_of_balls_3 constructs a rather large
triangulation internally to be able to mesh the union of ball. The block
will make sure that the destructor of union_of_balls is called and the
memory is freed. Especially since you have many points.

Could you check as well that the polyhedron is valid (p.is_valid())
after mesh_union_of_balls_3()? Just to make sure you have a valid
polyhedron to start the simplification with.

Nico

> 
On Wed, 2008-04-02 at 17:54 +0200, 

 wrote:
> I am having a problem operating on a union of balls mesh.  Code compiles 
> and runs without errors, but it seems when the number of vertices goes over 
> about 2 million, I get a run-time error if I either a)try to output the 
> mesh to an OFF or b) try to simplify the mesh using the mesh simplification 
> routine.  Code works fine when there is under 2 million vertices.  Here are 
> my constructors:
> 
> ///////////////////////
> typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
> typedef CGAL::Skin_surface_traits_3<K>                      Traits;
> typedef CGAL::Union_of_balls_3<Traits>                      
> Union_of_balls_3;
> typedef Union_of_balls_3::Weighted_point                    Weighted_point;
> typedef Weighted_point::Point                               Bare_point;
> typedef CGAL::Polyhedron_3<K,
>   CGAL::Skin_surface_polyhedral_items_3<Union_of_balls_3> >   Polyhedron;
> 
> namespace SMS = CGAL::Surface_mesh_simplification ;
> 
> Polyhedron p;
> //////////////////////
> 
> after adding the balls, here is my code to create the mesh and simplify, 
> just as with the related example from the manual:
> 
> ///////////////////////
>   Union_of_balls_3 union_of_balls(ball_set.begin(), ball_set.end(), 
> Traits(), true);
>   CGAL::mesh_union_of_balls_3(union_of_balls, p);
> 
>   SMS::Count_stop_predicate<Polyhedron> stop(ball_set.size());
>      
>   // This the actual call to the simplification algorithm.
>   // The surface and stop conditions are mandatory arguments.
>   // The index maps are needed because the vertices and edges
>   // of this surface lack an "id()" field.
>   int r = SMS::edge_collapse
>             (p
>             ,stop
>             ,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index, 
> p)) 
>                   .edge_index_map  (boost::get(CGAL::edge_external_index  , 
> p)) 
>             );
> 
>       std::ofstream out("output.off");
>         out << p;
> /////////////////////////
> 
> Is there some hard limit to the number of vertices that can be processed?  
> Am I using the wrong kernel?  Any help is appreciated.
> 
> BM