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

CGAL 4.8 - 2D Periodic Triangulations

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Periodic_2_triangulation_2/p2t2_covering.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Periodic_2_triangulation_traits_2.h>
#include <CGAL/Periodic_2_Delaunay_triangulation_2.h>
#include <iostream>
#include <vector>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Periodic_2_triangulation_traits_2<K> GT;
typedef CGAL::Periodic_2_Delaunay_triangulation_2<GT> PDT;
typedef PDT::Point Point;
typedef PDT::Covering_sheets Covering_sheets;
int main()
{
PDT T;
// Input point grid (27 points)
for (double x = 0. ; x < .9 ; x += 0.4)
{
for (double y = 0. ; y < .9 ; y += 0.4)
{
T.insert(Point(x, y));
}
}
Covering_sheets cs = T.number_of_sheets();
std::cout << "Current covering: " << cs[0] << ' ' << cs[1] << std::endl;
if ( T.is_triangulation_in_1_sheet() ) // = true
{
bool is_extensible = T.is_extensible_triangulation_in_1_sheet_h1()
|| T.is_extensible_triangulation_in_1_sheet_h2(); // = false
T.convert_to_1_sheeted_covering();
cs = T.number_of_sheets();
std::cout << "Current covering: " << cs[0] << ' ' << cs[1] << std::endl;
if ( is_extensible ) // = false
std::cout << "It is safe to change the triangulation here." << std::endl;
else
std::cout << "It is NOT safe to change the triangulation here!" << std::endl;
T.convert_to_9_sheeted_covering();
cs = T.number_of_sheets();
std::cout << "Current covering: " << cs[0] << ' ' << cs[1] << std::endl;
}
std::cout << "It is (again) safe to modify the triangulation." << std::endl;
return 0;
}