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RE: [cgal-discuss] Convex_hull_3 - CGAL


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  • From: Nuno Pessanha Santos <>
  • To: "" <>
  • Subject: RE: [cgal-discuss] Convex_hull_3 - CGAL
  • Date: Thu, 24 Oct 2013 21:41:38 +0100
  • Importance: Normal



Nuno Pessanha Santos 

Yes, -i really need speed in my implementation

I don´t know how to do it, but if you could give me more information I appreciate.

Thanks 

> From:
> To:
> CC:
> Date: Thu, 24 Oct 2013 21:08:50 +0200
> Subject: Re: [cgal-discuss] Convex_hull_3 - CGAL
>
> Nuno Pessanha Santos <> writes:
>
> > Thanks Sebastien.
> > For my implementation every millisecond counts, I have to implement that in the first way suggested by Sebastien.
> > 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;
> > 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"
>
> x is a member function. You need to actually call it to get x,
> e.g. chull_points[0].x().
>
> To get the behavior of indices you could extend the Point primitive of
> the kernel and add an index to it. That index would be preserved in the
> points of the Polyhedron, but this is rather tricky and I would only
> recommend trying it if you really need the speed.
>
> >
> >> 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
> >> > > >
> >> > > >
> >> > >
> >> > >
> >> > > --
> >> > > You are currently subscribed to cgal-discuss.
> >> > > To unsubscribe or access the archives, go to
> >> > > https://sympa.inria.fr/sympa/info/cgal-discuss
> >> > >
> >> > >
> >>
> >>
> >> --
> >> You are currently subscribed to cgal-discuss.
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> >>
> >>
>
> --
> Philipp Moeller
> GeometryFactory
>
> --
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