CGAL 5.6.3 - 2D Arrangements

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Arrangement_on_surface_2/face_extension.cpp
// Extending the arrangement-face records.
#include <CGAL/basic.h>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/Arr_observer.h>
#include "arr_exact_construction_segments.h"
typedef CGAL::Arr_face_extended_dcel<Traits, size_t> Dcel;
typedef CGAL::Arrangement_2<Traits, Dcel> Ex_arrangement;
// An arrangement observer, used to receive notifications of face splits and
// to update the indices of the newly created faces.
class Face_index_observer : public CGAL::Arr_observer<Ex_arrangement> {
private:
size_t n_faces; // the current number of faces
public:
Face_index_observer(Ex_arrangement& arr) :
CGAL::Arr_observer<Ex_arrangement>(arr), n_faces(0)
{
CGAL_precondition (arr.is_empty());
arr.unbounded_face()->set_data (0);
}
virtual void after_split_face(Face_handle, Face_handle new_face, bool)
{
new_face->set_data(++n_faces); // assign index to the new face
}
};
int main() {
// Construct the arrangement containing two intersecting triangles.
Ex_arrangement arr;
Face_index_observer obs(arr);
insert_non_intersecting_curve(arr, Segment(Point(4, 1), Point(7, 6)));
insert_non_intersecting_curve(arr, Segment(Point(1, 6), Point(7, 6)));
insert_non_intersecting_curve(arr, Segment(Point(4, 1), Point(1, 6)));
insert(arr, Segment(Point(1, 3), Point(7, 3)));
insert(arr, Segment(Point(1, 3), Point(4, 8)));
insert(arr, Segment(Point(4, 8), Point(7, 3)));
// Go over all arrangement faces and print the index of each face and its
// outer boundary. The face index is stored in the data field.
std::cout << arr.number_of_faces() << " faces:\n";
for (auto fit = arr.faces_begin(); fit != arr.faces_end(); ++fit) {
std::cout << "Face no. " << fit->data() << ": ";
if (fit->is_unbounded()) std::cout << "Unbounded.\n";
else {
auto curr = fit->outer_ccb();
std::cout << curr->source()->point();
do std::cout << " --> " << curr->target()->point();
while (++curr != fit->outer_ccb());
std::cout << std::endl;
}
}
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:244
CGAL::Arr_observer
Definition: Arr_observer.h:24
CGAL::Arr_observer::after_split_face
virtual void after_split_face(Face_handle f1, Face_handle f2, bool is_hole)
issued immediately after the existing face f1 has been split, such that a portion of it now forms a n...
CGAL::Arrangement_2
Definition: Arrangement_2.h:57