CGAL users discussion list

[Panagiotis Foteinos <>]

I found the source of the problem, and as is usually the case, it was
completely my fault.

The problem is that I did not use a Delaunay_d::Simplex_iterator to
traverse the Delaunay_d::simplices container, but a
Delaunay_d::Simplex.

I thought that if the cast succeeds, then it is safe to use a Simplex
instead of a Simplex_iterator. My mistake.

Thank you,
Panagiotis

On Tue, Jul 5, 2011 at 2:30 AM, Sebastien Loriot (GeometryFactory)
<>
 wrote:
> Panagiotis Foteinos wrote:
>>
>> Hello.
>>
>> I have encountered a problem with the Delaunay_d class, where d=4.
>>
>> I am reading the manual for Delaunay_d (
>>
>> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Convex_hull_d_ref/Class_Delaunay_d.html#Cross_link_anchor_983
>> ), and it seems that there is no way to test if a simplex is infinite
>> or not. So, I am guessing that there are no infinite simplices.
>> Therefore, after the insertion of 5 (linearly independent) Point_d
>> points, I expect to see just one simplex.
>>
>> However, when I get the simplices in Delaunay_d::simplices_begin()
>> ---> Delaunay_d::simplices_end(), I count 6 simplices. Are the 5 extra
>> simplices the infinite simplices? If so, how do I check whether a
>> simplex is infinite or not?
>>
>> The problem is observed with the insertion of the following sequence
>> of 4D points:
>>
>> (1.0/sqrt(10), 1.0/sqrt(6), 1.0/sqrt(3), 1)
>> (1.0/sqrt(10), 1.0/sqrt(6), 1/sqrt(3), -1)
>> (1.0/sqrt(10), 1.0/sqrt(6), -2.0/sqrt(3), -0)
>> (1.0/sqrt(10),-sqrt(3.0/2), 0, 0)
>> (-2*sqrt(2.0/5), 0, 0, 0)
>>
>>
>> Best Regards,
>> Panagiotis Foteinos
>>
>
> On my machine the result is fine (one simplex). How did you construct
> the 4D points? You should use the constructor
> template <class InputIterator>
> Point_d<Kernel> p ( int d, InputIterator first, InputIterator last);
>
> the one with four arguments builds 3D points with homogeneous coordinates.
>
> Sebastien.
>
> #include <CGAL/Cartesian_d.h>
> #include <CGAL/Gmpq.h>
> #include <CGAL/Delaunay_d.h>
> #include <iostream>
>
> typedef CGAL::Gmpq FT;
> typedef CGAL::Cartesian_d<FT> Kernel;
> typedef CGAL::Delaunay_d<Kernel> Delaunay_d;
> typedef Delaunay_d::Point_d Point_d;
> typedef Delaunay_d::Simplex_handle Simplex_handle;
> typedef Delaunay_d::Vertex_handle Vertex_handle;
>
> int main()
> {
>  Delaunay_d T(4);
>  FT points[5][4]={
>    {FT(1.0/sqrt(10)), FT(1.0/sqrt(6)), FT(1.0/sqrt(3)), FT(1)},
>    {FT(1.0/sqrt(10)), FT(1.0/sqrt(6)), FT(1/sqrt(3)), FT(-1)},
>    {FT(1.0/sqrt(10)), FT(1.0/sqrt(6)), FT(-2.0/sqrt(3)), FT(-0)},
>    {FT(1.0/sqrt(10)),FT(-sqrt(3.0/2)), FT(0), FT(0)},
>    {FT(-2*sqrt(2.0/5)), FT(0), FT(0), FT(0)}
>  };
>
>  T.insert(Point_d(4,points[0],points[0]+4));
>  T.insert(Point_d(4,points[1],points[1]+4));
>  T.insert(Point_d(4,points[2],points[2]+4));
>  T.insert(Point_d(4,points[3],points[3]+4));
>  T.insert(Point_d(4,points[4],points[4]+4));
>
>  int index=0;
>  Delaunay_d::Simplex_iterator it=T.simplices_begin();
>  for(;it!=T.simplices_end();++it,++index);
>
>  std::cout << index << std::endl;
> }
>
>
> --
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://lists-sop.inria.fr/wws/info/cgal-discuss
>
>