CGAL 5.4.1 - 2D Arrangements
Arrangement_on_surface_2/dcel_extension_io.cpp
// Using the I/O operators for arrangements with extended DCEL records.
#include <fstream>
#include <CGAL/basic.h>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/IO/Arr_iostream.h>
#include <CGAL/IO/Arr_text_formatter.h>
#include "arr_exact_construction_segments.h"
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::Arrangement_2<Traits, Ext_dcel> Ext_arrangement;
int main() {
// Construct the arrangement containing two intersecting triangles.
Ext_arrangement arr;
Segment s1(Point(4, 1), Point(7, 6));
Segment s2(Point(1, 6), Point(7, 6));
Segment s3(Point(4, 1), Point(1, 6));
Segment s4(Point(1, 3), Point(7, 3));
Segment s5(Point(1, 3), Point(4, 8));
Segment s6(Point(4, 8), Point(7, 3));
insert(arr, s4);
insert(arr, s5);
insert(arr, s6);
// Go over all arrangement vertices and set their colors.
for (auto vit = arr.vertices_begin(); vit != arr.vertices_end(); ++vit) {
auto 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.
for (auto eit = arr.edges_begin(); eit != arr.edges_end(); ++eit) {
// Check if the halfedge has the same direction as its associated
// segment. Note that its twin always has an opposite direction.
auto 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.
int boundary_size;
for (auto fit = arr.faces_begin(); fit != arr.faces_end(); ++fit) {
boundary_size = 0;
if (! fit->is_unbounded()) {
auto curr = fit->outer_ccb();
do ++boundary_size;
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;
CGAL::IO::write(arr, out_file, formatter);
out_file.close();
// Read the arrangement from the file.
Ext_arrangement arr2;
std::ifstream in_file("arr_ex_dcel_io.dat");
CGAL::IO::read(arr2, in_file, formatter);
in_file.close();
std::cout << "The arrangement vertices:\n";
for (auto vit = arr2.vertices_begin(); vit != arr2.vertices_end(); ++vit)
std::cout << '(' << vit->point() << ") - " << vit->data() << std::endl;
return 0;
}