CGAL users discussion list

[Camille Wormser <>]

 wrote:

> Can anyone please provide me with a simple example to calculate the convex 
> hull of a set of points in 6D, USING CGAL ?
>  
Something like this should work :
--------------------------------------------------------------------
#include <list>
#include <Convex_hull_d.h>
#include <CGAL/Cartesian_d.h>

typedef CGAL::Cartesian_d<double>                            Kd;
typedef CGAL::Convex_hull_d<Kd>                          CHull_d;
typedef CHull_d::Point_d                                 Point_d;
typedef std::list<Point_d>                               List_ptd;

CHull_d* init_insertion(List_ptd points) {
   CHull_d::Vertex_handle vh6;
   List_ptd::iterator a, b;

   a = points->begin();
   b = points->end();
   ch6 = new CHull_d(6);

   while(a != b) {
       vh6 = ch6->insert(*a);
   ++a;
   }
}
--------------------------------------------------------------------
A Point_d can be created by calling for example
Point_d(6, c.begin(), c.end());
where c is a list of 6 doubles.

Then, if you want to retrieve the points on the convex hull, you have 
access to iterators
ch6->Hull_point_const_iterator hull_points_begin()
ch6->Hull_point_const_iterator hull_points_end()

You also have the facets iterators
ch6->Facet_iterator facets_begin()
ch6->Facet_iterator facets_end()

and ch6->vertex_of_facet(facet,j) for j = 0..5 gives you the vertices.
ch6->vertex_of_facet(facet,j)->point() gives you the point.
ch6->vertex_of_facet(facet,j)->point().cartesian_begin() gives you an 
iterator on the coordinates.

You may however soon encounter robustness issues, and then need an exact 
number type (note that this Convex_hull_d computes and stores some 
hyperplanes, and is not completely predicate-based...).
--
Camille