CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 10/24/2013 05:22 PM, Nuno Pessanha Santos wrote:
> Thanks Sebastien.
>
> For my implementation every millisecond counts, I have to implement that
> in the first way suggested by Sebastien.
One way to go is to define a new model of ConvexHullTraits_3 with 
std::size_t as point type. Then you redefine all the predicates by
forwarding to the default traits class, and the polyhedron points
will then be the indices.

> Another question,I hope the final one.
>
> When I make:
>
> CGAL::convex_hull_3(points.begin(), points.end(), poly);
> std::vector<Point_3> chull_points(poly.points_begin(), poly.points_end());
>
> It´s not suppose to access the point 0 coordinate X by the:
> std::cout << chull_points[0].x;

it's a function:
chull_points[0].x()

Sebastien.

> This gives me the error:
>
> "error C3867: 'CGAL::Point_3<R_>::x': function call missing argument
> list; use '&CGAL::Point_3<R_>::x' to create a pointer to member"
>
> Thanks.
>
> Nuno Pessanha Santos
>
>
>
>
>  > Date: Thu, 24 Oct 2013 16:51:32 +0200
>  > From: 
>
>  > To: 
>
>  > Subject: Re: [cgal-discuss] Convex_hull_3 - CGAL
>  >
>  > The only way to do it for now I think is to use the Delaunay
>  > triangulation.
>  > Note that it will take more time to compute than the other function.
>  > (I'll add a todo for adding this in a future release)
>  >
>  > Build the triangulation following this example:
>  >
> http://doc.cgal.org/latest/Triangulation_3/index.html#Triangulation_3UsingtheBoostTransformIterator
>  >
>  > Then something like this should work (not tested):
>  >
>  > struct Chull_indices
>  > {
>  > void operator()(Delaunay::Vertex_handle vh) const
>  > {
>  > m_indices.push_back(vh->info());
>  > }
>  >
>  > std::vector<std::size_t> m_indices;
>  > };
>  >
>  > Chull_indices chull_indices;
>  >
>  > T.adjacent_vertices(T.infinite_vertex(),
>  > boost::make_function_output_iterator(chull_indices)
>  > );
>  >
>  > for( std::size_t i : chull_indices.m_indices)
>  > std::cout << i << std::endl;
>  >
>  > Sebastien.
>  >
>  > On 10/24/2013 04:12 PM, Nuno Pessanha Santos wrote:
>  > > Hi,
>  > >
>  > > Thanks Sebastien for your answer.
>  > >
>  > > I only need the index of the points, example:
>  > >
>  > > Original Point Cloud:
>  > > point 1
>  > > point 2
>  > > point 3
>  > > point 4
>  > >
>  > > Convex Hull:
>  > > point 3
>  > > point 4
>  > >
>  > > I want to read the 3 and 4, to make them correspond in my further
>  > > processing.
>  > >
>  > > Thanks.
>  > >
>  > > Nuno Pessanha Santos
>  > >
>  > >
>  > >
>  > >
>  > > > Date: Thu, 24 Oct 2013 07:11:37 +0200
>  > > > From: 
>
>  > > > To: 
>
>  > > > Subject: Re: [cgal-discuss] Convex_hull_3 - CGAL
>  > > >
>  > > > On 10/24/2013 05:31 AM, Nuno Pessanha Santos wrote:
>  > > > > Hi,
>  > > > >
>  > > > > I am starting to use CGAL, and maybe this is a stupid question
> but I
>  > > > > need some help.
>  > > > >
>  > > > > When you use the function "CGAL::convex_hull_3(points.begin(),
>  > > > > points.end(), Polyhedron_3 poly);" you obtain the polyhedron poly.
>  > > > >
>  > > > > How can I read the obtained vertices or the points index that are
>  > > > > contained in the convex hull? I see so many examples but none
> of them
>  > > > > could help me in my task.
>  > > >
>  > > > Is the following what you are looking for?
>  > > >
>  > > > Polyhedron_3 poly;
>  > > > CGAL::convex_hull_3(points.begin(), points.end(), poly);
>  > > > std::vector<Point_3> chull_points(poly.points_begin(),
>  > > poly.points_end());
>  > > >
>  > > >
>  > > > Sebastien
>  > > >
>  > > > >
>  > > > > Thanks
>  > > > >
>  > > > > Nuno Pessanha Santos
>  > > > >
>  > > > >
>  > > >
>  > > >
>  > > > --
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>  > > >
>  >
>  >
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