CGAL users discussion list

[Laurent Rineau <>]

On Monday 06 August 2007 12:05:33 Tyver Ray wrote:
> Hello!
>
> Thank you for the answer. My problem is that I do not know how I can use it
> with my definitions :
>
> struct    K : CGAL::Exact_predicates_inexact_constructions_kernel {};
> typedef CGAL::Triangulation_euclidean_traits_xy_3<K>    Gt;
> typedef CGAL::Triangulation_vertex_base_2<Gt>              Vb;
> typedef CGAL::Triangulation_face_base_2<Gt>                Fb;
> typedef CGAL::Triangulation_data_structure_2<Vb,Fb>     Tds;
> typedef CGAL::Point_set_2<Gt, Tds>                              PS;
> typedef CGAL::Delaunay_triangulation_2<Gt, Tds>           Delaunay;
>
> typedef K::Point_2                                        Point2;
> typedef K::Point_3                                        Point3;
> typedef K::Circle_2                                       Circle;
>
>
> First, in the documentation it is said that I have to define a Gt::Circle_2
> but with my triangulation I'm obliged to get it through the Kernel because
> of my Triangulation_euclidean_traits_xy_3<K> Gt.

Well, that traits class Triangulation_euclidean_traits_xy_3<K> was designed 
for 2D Delaunay triangulations, and has not been adapted to 
Point_set_2<Gt,Tds>. You need to amend that class, so that it is a model of 
the concept PointSetTraits:

http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Point_set_2_ref/Concept_PointSetTraits.html

A few types and predicates need to be added:
  Bounded_side_2
  Circle_2
  Compare_distance_2
  Compute_squared_distance_2
  Construct_center_2
  Construct_circle_2
  FT

It should not be too difficult, as long as you use the distance in the plane 
xy. Circle_2 is K::Circle_3. Compute_squared_distance_2, Construct_center_2, 
and Construct_circle_2 are strait-forward (construct the circle in the 
xy-plane). Bounded_side_2 and Compare_distance_2 need to be adapted: see the 
other predicates of the traits class.

If you need to use the euclidean 3D distance, then I think that Point_set_2 
is 
not the solution.

-- 
Laurent Rineau
INRIA - Sophia Antipolis
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