\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - 2D Arrangements

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Arrangement_on_surface_2/dcel_extension_io.cpp
// Using the I/O operators for arrangements with extended DCEL records.
#include <CGAL/Cartesian.h>
#include <CGAL/Exact_rational.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/Arrangement_2.h>
#include <CGAL/IO/Arr_text_formatter.h>
#include <CGAL/IO/Arr_iostream.h>
#include <fstream>
enum Color {BLUE, RED, WHITE};
std::ostream& operator<< (std::ostream& os, const Color& color)
{
switch (color)
{
case BLUE: os << "BLUE"; break;
case RED: os << "RED"; break;
case WHITE: os << "WHITE"; break;
default: os << "ERROR!";
}
return (os);
}
std::istream& operator>> (std::istream& is, Color& color)
{
std::string str;
is >> str;
if (str == "BLUE")
color = BLUE;
else if (str == "RED")
color = RED;
else if (str == "WHITE")
color = WHITE;
return (is);
}
typedef CGAL::Cartesian<CGAL::Exact_rational> Kernel;
typedef CGAL::Arr_segment_traits_2<Kernel> Traits_2;
typedef Traits_2::Point_2 Point_2;
typedef Traits_2::X_monotone_curve_2 Segment_2;
typedef CGAL::Arr_extended_dcel<Traits_2,
Color, bool, int> Dcel;
typedef CGAL::Arrangement_2<Traits_2, Dcel> Arrangement_2;
typedef CGAL::Arr_extended_dcel_text_formatter<Arrangement_2> Formatter;
int main ()
{
// Construct the arrangement containing two intersecting triangles.
Arrangement_2 arr;
Segment_2 s1 (Point_2(4, 1), Point_2(7, 6));
Segment_2 s2 (Point_2(1, 6), Point_2(7, 6));
Segment_2 s3 (Point_2(4, 1), Point_2(1, 6));
Segment_2 s4 (Point_2(1, 3), Point_2(7, 3));
Segment_2 s5 (Point_2(1, 3), Point_2(4, 8));
Segment_2 s6 (Point_2(4, 8), Point_2(7, 3));
insert_non_intersecting_curve (arr, s1);
insert_non_intersecting_curve (arr, s2);
insert_non_intersecting_curve (arr, s3);
insert (arr, s4);
insert (arr, s5);
insert (arr, s6);
// Go over all arrangement vertices and set their colors.
Arrangement_2::Vertex_iterator vit;
std::size_t degree;
for (vit = arr.vertices_begin(); vit != arr.vertices_end(); ++vit)
{
degree = vit->degree();
if (degree == 0)
vit->set_data (BLUE); // Isolated vertex.
else if (degree <= 2)
vit->set_data (RED); // Vertex represents an endpoint.
else
vit->set_data (WHITE); // Vertex represents an intersection point.
}
// Go over all arrangement edges and set their flags.
Arrangement_2::Edge_iterator eit;
bool flag;
for (eit = arr.edges_begin(); eit != arr.edges_end(); ++eit)
{
// Check if the halfegde has the same diretion as its associated
// segment. Note that its twin always has an opposite direction.
flag = (eit->source()->point() == eit->curve().source());
eit->set_data (flag);
eit->twin()->set_data (!flag);
}
// Go over all arrangement faces and print their outer boundary and indices.
Arrangement_2::Face_iterator fit;
Arrangement_2::Ccb_halfedge_circulator curr;
int boundary_size;
for (fit = arr.faces_begin(); fit != arr.faces_end(); ++fit)
{
boundary_size = 0;
if (! fit->is_unbounded())
{
curr = fit->outer_ccb();
do
{
++boundary_size;
++curr;
} while (curr != fit->outer_ccb());
}
fit->set_data (boundary_size);
}
// Write the arrangement to a file.
std::ofstream out_file ("arr_ex_dcel_io.dat");
Formatter formatter;
write (arr, out_file, formatter);
out_file.close();
// Read the arrangement from the file.
Arrangement_2 arr2;
std::ifstream in_file ("arr_ex_dcel_io.dat");
read (arr2, in_file, formatter);
in_file.close();
std::cout << "The arrangement vertices: " << std::endl;
for (vit = arr2.vertices_begin(); vit != arr2.vertices_end(); ++vit)
std::cout << '(' << vit->point() << ") - " << vit->data() << std::endl;
return (0);
}