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CGAL 4.8 - 2D Arrangements

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Arrangement_on_surface_2/consolidated_curve_data.cpp
// Associating a color attribute with segments using the consolidated
// curve-data traits.
#include <CGAL/Cartesian.h>
#include <CGAL/Exact_rational.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arr_consolidated_curve_data_traits_2.h>
#include <CGAL/Arrangement_2.h>
#include <CGAL/Arr_landmarks_point_location.h>
enum Segment_color {
RED,
BLUE
};
typedef CGAL::Cartesian<CGAL::Exact_rational> Kernel;
typedef CGAL::Arr_segment_traits_2<Kernel> Segment_traits_2;
typedef Segment_traits_2::Curve_2 Segment_2;
typedef CGAL::Arr_consolidated_curve_data_traits_2
<Segment_traits_2, Segment_color> Traits_2;
typedef Traits_2::Point_2 Point_2;
typedef Traits_2::Curve_2 Colored_segment_2;
typedef CGAL::Arrangement_2<Traits_2> Arrangement_2;
typedef CGAL::Arr_landmarks_point_location<Arrangement_2> Landmarks_pl;
int main ()
{
// Construct an arrangement containing three RED line segments.
Arrangement_2 arr;
Landmarks_pl pl (arr);
Segment_2 s1 (Point_2(-1, -1), Point_2(1, 3));
Segment_2 s2 (Point_2(2, 0), Point_2(3, 3));
Segment_2 s3 (Point_2(0, 3), Point_2(2, 5));
insert (arr, Colored_segment_2 (s1, RED), pl);
insert (arr, Colored_segment_2 (s2, RED), pl);
insert (arr, Colored_segment_2 (s3, RED), pl);
// Insert three BLUE line segments.
Segment_2 s4 (Point_2(-1, 3), Point_2(4, 1));
Segment_2 s5 (Point_2(-1, 0), Point_2(4, 1));
Segment_2 s6 (Point_2(-2, 1), Point_2(1, 4));
insert (arr, Colored_segment_2 (s4, BLUE), pl);
insert (arr, Colored_segment_2 (s5, BLUE), pl);
insert (arr, Colored_segment_2 (s6, BLUE), pl);
// Go over all vertices and print just the ones corresponding to intersection
// points between RED segments and BLUE segments. Note that we skip endpoints
// of overlapping sections.
Arrangement_2::Vertex_const_iterator vit;
Segment_color color;
for (vit = arr.vertices_begin(); vit != arr.vertices_end(); ++vit) {
// Go over the incident halfedges of the current vertex and examine their
// colors.
bool has_red = false;
bool has_blue = false;
Arrangement_2::Halfedge_around_vertex_const_circulator eit, first;
eit = first = vit->incident_halfedges();
do {
// Get the color of the current half-edge.
if (eit->curve().data().size() == 1) {
color = eit->curve().data().front();
if (color == RED)
has_red = true;
else if (color == BLUE)
has_blue = true;
}
++eit;
} while (eit != first);
// Print the vertex only if incident RED and BLUE edges were found.
if (has_red && has_blue)
{
std::cout << "Red-blue intersection at (" << vit->point() << ")"
<< std::endl;
}
}
// Locate the edges that correspond to a red-blue overlap.
Arrangement_2::Edge_iterator eit;
for (eit = arr.edges_begin(); eit != arr.edges_end(); ++eit)
{
// Go over the incident edges of the current vertex and examine their
// colors.
bool has_red = false;
bool has_blue = false;
Traits_2::Data_container::const_iterator dit;
for (dit = eit->curve().data().begin(); dit != eit->curve().data().end();
++dit)
{
if (*dit == RED)
has_red = true;
else if (*dit == BLUE)
has_blue = true;
}
// Print the edge only if it corresponds to a red-blue overlap.
if (has_red && has_blue)
std::cout << "Red-blue overlap at [" << eit->curve() << "]" << std::endl;
}
return 0;
}