CGAL users discussion list

[Efi Fogel <>]

Hi Marek,

First, if you don't have holes why define an object of type Polygon_with_holes?

Anyhow, if you insists, you can define a polygon with hole like so:

  Polygon_with_holes_2 P;
  P.outer_boundary().push_back(Point_2(-3., -3.));
  P.outer_boundary().push_back(Point_2(7., -3.));
  P.outer_boundary().push_back(Point_2(7., 7.));
  P.outer_boundary().push_back(Point_2(-3., 7.));

  // the hole for the polygon to apply Q
  Polygon_2 hole;
  hole.push_back(Point_2(5., 2.));
  hole.push_back(Point_2(2., 2.));
  hole.push_back(Point_2(2., 5.));
  hole.push_back(Point_2(5., 5.));
  P.add_hole(hole);

Best,

Efi

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On 13 November 2017 at 18:25, xoru <> wrote:

I'm beginer with cgal. I need add 2 boxes and get one rectangles (created from 4 points).
My objects 2d are polygons with holes or not. I dont know how setting 'empty' holes list.
How I must writing this code correctly?

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Boolean_set_operations_2.h>
#include <list>
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef Kernel::Point_2 Point_2;
typedef CGAL::Polygon_2<Kernel> Polygon_2;
typedef CGAL::Polygon_with_holes_2<Kernel> Polygon_with_holes_2;
typedef std::list<Polygon_with_holes_2> Pwh_list_2;
#include "print_utils.h"
int main ()
{
Polygon_2 outP;
Polygon_2 holesP[1];
outP.push_back (Point_2 (0, 0));
outP.push_back (Point_2 (1, 0));
outP.push_back (Point_2 (1, 1));
outP.push_back (Point_2 (0, 1));
Polygon_with_holes_2 P (outP, holesP, holesP + 1);
Polygon_2 outQ;
Polygon_2 holesQ[1];
outQ.push_back (Point_2 (1, 0));
outQ.push_back (Point_2 (2, 0));
outQ.push_back (Point_2 (2, 1));
outQ.push_back (Point_2 (1, 1));
/* without holes */
Polygon_with_holes_2 Q (outQ, holesQ, holesQ + 1);
std::cout << "Q = "; print_polygon_with_holes (Q);
// How check orientation, simple etc. I dont know the orientation is good
// if(P.is_simple){ std::cout << "P is simple.\n"; }
Polygon_with_holes_2 unionR;
if (CGAL::join (P, Q, unionR))
{
print_polygon_with_holes (unionR);
}
else
{
/* how add P and Q (union P and Q) */
}
return 0;
}
Thanks
Marek