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

CGAL 4.8 - Triangulated Surface Mesh Segmentation

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Surface_mesh_segmentation/segmentation_with_facet_ids_example.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/boost/graph/graph_traits_Polyhedron_3.h>
#include <CGAL/Polyhedron_items_with_id_3.h>
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/mesh_segmentation.h>
#include <CGAL/property_map.h>
#include <iostream>
#include <fstream>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Polyhedron_3<K, CGAL::Polyhedron_items_with_id_3> Polyhedron;
// Property map associating a facet with an integer as id to an
// element in a vector stored internally
template<class ValueType>
struct Facet_with_id_pmap
: public boost::put_get_helper<ValueType&,
Facet_with_id_pmap<ValueType> >
{
typedef Polyhedron::Facet_const_handle key_type;
typedef ValueType value_type;
typedef value_type& reference;
typedef boost::lvalue_property_map_tag category;
Facet_with_id_pmap(
std::vector<ValueType>& internal_vector
) : internal_vector(internal_vector) { }
reference operator[](key_type key) const
{ return internal_vector[key->id()]; }
private:
std::vector<ValueType>& internal_vector;
};
int main()
{
// create and read Polyhedron
Polyhedron mesh;
std::ifstream input("data/cactus.off");
if ( !input || !(input >> mesh) || mesh.empty() ) {
std::cerr << "Not a valid off file." << std::endl;
return EXIT_FAILURE;
}
// assign id field for each facet
std::size_t facet_id = 0;
for(Polyhedron::Facet_iterator facet_it = mesh.facets_begin();
facet_it != mesh.facets_end(); ++facet_it, ++facet_id) {
facet_it->id() = facet_id;
}
// create a property-map for SDF values
std::vector<double> sdf_values(mesh.size_of_facets());
Facet_with_id_pmap<double> sdf_property_map(sdf_values);
CGAL::sdf_values(mesh, sdf_property_map);
// access SDF values (with constant-complexity)
for(Polyhedron::Facet_const_iterator facet_it = mesh.facets_begin();
facet_it != mesh.facets_end(); ++facet_it) {
std::cout << sdf_property_map[facet_it] << " ";
}
std::cout << std::endl;
// create a property-map for segment-ids
std::vector<std::size_t> segment_ids(mesh.size_of_facets());
Facet_with_id_pmap<std::size_t> segment_property_map(segment_ids);
CGAL::segmentation_from_sdf_values(mesh, sdf_property_map, segment_property_map);
// access segment-ids (with constant-complexity)
for(Polyhedron::Facet_const_iterator facet_it = mesh.facets_begin();
facet_it != mesh.facets_end(); ++facet_it) {
std::cout << segment_property_map[facet_it] << " ";
}
std::cout << std::endl;
}