CGAL 6.2 - Surface Mesh Topology

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Surface_mesh_topology/shortest_noncontractible_cycle.cpp
#include <CGAL/Linear_cell_complex_for_combinatorial_map.h>
#include <CGAL/Linear_cell_complex_constructors.h>
#include <CGAL/Curves_on_surface_topology.h>
#include <CGAL/Path_on_surface.h>
#include <CGAL/draw_face_graph_with_paths.h>
#include <CGAL/Random.h>
#include <iostream>
#include <cstdlib>
using LCC_3 =CGAL::Linear_cell_complex_for_combinatorial_map<2, 3>;
using Path_on_surface=CGAL::Surface_mesh_topology::Path_on_surface<LCC_3>;
double cycle_length(const LCC_3& lcc, const Path_on_surface& cycle)
{ // Compute the length of the given cycle.
double res=0;
for (std::size_t i=0; i<cycle.length(); ++i)
{ res+=std::sqrt
(CGAL::squared_distance(lcc.point(cycle[i]),
lcc.point(lcc.other_extremity(cycle[i])))); }
return res;
}
void display_cycle_info(const LCC_3& lcc, const Path_on_surface& cycle)
{ // Display information about the given cycle.
if (cycle.is_empty()) { std::cout<<"Empty."<<std::endl; return; }
std::cout<<"Root: "<<lcc.point(cycle[0])<<"; "
<<"Number of edges: "<<cycle.length()<<"; "
<<"Length: "<<cycle_length(lcc, cycle)<<std::endl;
}
int main(int argc, char* argv[])
{
std::string filename(argc==1?CGAL::data_file_path("meshes/3torus.off"):argv[1]);
bool draw=(argc<3?false:std::string(argv[2])=="-draw");
LCC_3 lcc;
if (!CGAL::load_off(lcc, filename.c_str())) // Load the off file.
{
std::cout<<"Cannot read file '"<<filename<<"'. Exiting program"<<std::endl;
return EXIT_FAILURE;
}
std::cout<<"File '"<<filename<<"' loaded. Finding shortest non contractible cycle..."<<std::endl;
CGAL::Surface_mesh_topology::Curves_on_surface_topology<LCC_3> cst(lcc);
LCC_3::Dart_const_descriptor root=lcc.dart_descriptor
(CGAL::get_default_random().get_int(0, static_cast<int>(lcc.number_of_darts()))); // One dart of the mesh
Path_on_surface cycle1=
cst.compute_shortest_non_contractible_cycle_with_base_point(root);
CGAL::Surface_mesh_topology::Euclidean_length_weight_functor<LCC_3> wf(lcc);
Path_on_surface cycle2=
cst.compute_shortest_non_contractible_cycle_with_base_point(root, wf);
std::cout<<"Cycle 1 (pink): "; display_cycle_info(lcc, cycle1);
std::cout<<"Cycle 2 (green): "; display_cycle_info(lcc, cycle2);
if (draw)
{
auto cycles={cycle1, cycle2};
CGAL::draw(lcc, cycles);
}
return EXIT_SUCCESS;
}
CGAL::Linear_cell_complex_for_combinatorial_map
CGAL::Surface_mesh_topology::Curves_on_surface_topology
The class Curves_on_surface_topology provides methods to compute shortest non contractible cycles and...
Definition: Curves_on_surface_topology.h:13
CGAL::Surface_mesh_topology::Path_on_surface
The class Path_on_surface represents a walk in a mesh which is either a model of CombinatorialMap,...
Definition: Path_on_surface.h:13
CGAL::draw
void draw(const LCC &lcc, const GSOptions &gso)
draw
void draw(const SM &sm, const GSOptions &gso)
CGAL::Surface_mesh_topology::Euclidean_length_weight_functor
A model of WeightFunctor assigning its Euclidean length to every edge.
Definition: Curves_on_surface_topology.h:90