CGAL 6.1 - 2D Arrangements

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Arrangement_on_surface_2/overlay_unbounded.cpp
// A face overlay of two arrangements with unbounded faces.
#include <string>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/Arr_overlay_2.h>
#include <CGAL/Arr_default_overlay_traits.h>
#include "arr_linear.h"
// Define a functor for creating a label from a character and an integer.
struct Overlay_label {
std::string operator()(char c, unsigned int i) const
{ return c + std::to_string(i); }
};
using Dcel_dlue = CGAL::Arr_face_extended_dcel<Traits, char>;
using Arrangement_blue = CGAL::Arrangement_2<Traits, Dcel_dlue>;
using Dcel_red = CGAL::Arr_face_extended_dcel<Traits, unsigned int>;
using Arrangement_red = CGAL::Arrangement_2<Traits, Dcel_red>;
using Dcel_res = CGAL::Arr_face_extended_dcel<Traits, std::string>;
using Arrangement_res = CGAL::Arrangement_2<Traits, Dcel_res>;
using Overlay_traits =
CGAL::Arr_face_overlay_traits<Arrangement_blue, Arrangement_red,
Arrangement_res, Overlay_label>;
int main() {
// Construct the first arrangement, induced by two lines y = x and y = -x.
Arrangement_blue arr1;
insert(arr1, Line(Point(0, 0), Point(1, 1)));
insert(arr1, Line(Point(0, 0), Point(1, -1)));
// Label the four (unbounded) faces of the arrangement as 'A' to 'D' by
// traversing the faces incident to the halfedges around the single
// arrangement vertex (0, 0).
char clabel = 'A';
auto first = arr1.vertices_begin()->incident_halfedges();
auto curr = first;
do curr->face()->set_data(clabel++);
while (++curr != first);
// Construct the second arrangement, containing a single square-shaped face.
Arrangement_red arr2;
insert_non_intersecting_curve(arr2, Segment(Point(-3, -3), Point(3, -3)));
insert_non_intersecting_curve(arr2, Segment(Point(3, -3), Point(3, 3)));
insert_non_intersecting_curve(arr2, Segment(Point(3, 3), Point(-3, 3)));
insert_non_intersecting_curve(arr2, Segment(Point(-3, 3), Point(-3, -3)));
// Give the unbounded face the index 1, and the bounded face the index 2.
for (auto fit = arr2.faces_begin(); fit != arr2.faces_end(); ++fit)
fit->set_data((fit == arr2.unbounded_face()) ? 1 : 2);
// Compute the overlay of the two arrangements.
Arrangement_res overlay_arr;
Overlay_traits overlay_traits;
CGAL::overlay(arr1, arr2, overlay_arr, overlay_traits);
// Go over the faces of the overlay arrangement and print their labels.
std::cout << "The overlay faces are:\n";
for (auto res_fit = overlay_arr.faces_begin();
res_fit != overlay_arr.faces_end(); ++res_fit)
{
std::cout << " " << res_fit->data().c_str() << " ("
<< (res_fit->is_unbounded() ? "unbounded" : "bounded") << ").\n";
}
return 0;
}
CGAL::Arr_face_extended_dcel
The Arr_face_extended_dcel class-template extends the DCEL face-records, making it possible to store ...
Definition: Arr_extended_dcel.h:206
CGAL::Arr_face_overlay_traits
An instance of Arr_face_overlay_traits should be used for overlaying two arrangements of types Arr_A ...
Definition: Arr_default_overlay_traits.h:43
CGAL::Arrangement_2
Definition: Arrangement_2.h:57
CGAL::overlay
void overlay(const Arrangement_2< GeomTraitsA, TopTraitsA > &arr1, const Arrangement_2< GeomTraitsB, TopTraitsB > &arr2, Arrangement_2< GeomTraitsRes, TopTraitsRes > &arr_res, OverlayTraits &ovl_tr)
Computes the overlay of two arrangements arr1 and arr2, and sets the output arrangement res to repres...