CGAL 6.1.1 - 2D Arrangements

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Arrangement_on_surface_2/bounded_vertical_decomposition.cpp
// Performing vertical decomposition of an arrangement.
#include <list>
#include <CGAL/Arr_vertical_decomposition_2.h>
#include "arr_exact_construction_segments.h"
using Object_pair = std::pair<CGAL::Object, CGAL::Object>;
using Vert_decomp_entry = std::pair<Vertex_const_handle, Object_pair>;
using Vert_decomp_list = std::list<Vert_decomp_entry>;
int main() {
// Construct the arrangement.
Segment segments[] = {Segment(Point(0, 0), Point(3, 3)),
Segment(Point(3, 3), Point(6, 0)),
Segment(Point(2, 0), Point(5, 3)),
Segment(Point(5, 3), Point(8, 0))};
Arrangement arr;
insert(arr, segments, segments + sizeof(segments)/sizeof(Segment));
// Perform vertical ray-shooting from every vertex and locate the feature
// that lie below it and the feature that lies above it.
Vert_decomp_list vd_list;
CGAL::decompose(arr, std::back_inserter(vd_list));
// Print the results.
for (auto vd_iter = vd_list.begin(); vd_iter != vd_list.end(); ++vd_iter) {
const Object_pair& curr = vd_iter->second;
std::cout << "Vertex (" << vd_iter->first->point() << ") : ";
Vertex_const_handle vh;
Halfedge_const_handle hh;
Face_const_handle fh;
std::cout << " feature below: ";
if (CGAL::assign(hh, curr.first)) std::cout << '[' << hh->curve() << ']';
else if (CGAL::assign(vh, curr.first))
std::cout << '(' << vh->point() << ')';
else if (CGAL::assign(fh, curr.first)) std::cout << "NONE";
else std::cout << "EMPTY";
std::cout << " feature above: ";
if (CGAL::assign(hh, curr.second))
std::cout << '[' << hh->curve() << "]\n";
else if (CGAL::assign(vh, curr.second))
std::cout << '(' << vh->point() << ")\n";
else if (CGAL::assign(fh, curr.second)) std::cout << "NONE\n";
else std::cout << "EMPTY\n";
}
return 0;
}
CGAL::decompose
OutputIterator decompose(const Arrangement_on_surface_2< GeometryTraits, TopologyTraits > &arr, OutputIterator oi)
produces the symbolic vertical decomposition of a given arrangement.