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

CGAL 4.8 - Triangulated Surface Mesh Skeletonization

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Surface_mesh_skeletonization/segmentation_example.cpp
#include <CGAL/Polyhedron_3.h>
#include <CGAL/Polyhedron_items_with_id_3.h>
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/boost/graph/graph_traits_Polyhedron_3.h>
#include <CGAL/Simple_cartesian.h>
#include <CGAL/extract_mean_curvature_flow_skeleton.h>
#include <CGAL/mesh_segmentation.h>
#include <fstream>
typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_3 Point;
typedef CGAL::Polyhedron_3<Kernel, CGAL::Polyhedron_items_with_id_3> Polyhedron;
typedef boost::graph_traits<Polyhedron>::vertex_descriptor vertex_descriptor;
typedef boost::graph_traits<Polyhedron>::halfedge_descriptor halfedge_descriptor;
typedef boost::graph_traits<Polyhedron>::face_descriptor face_descriptor;
typedef CGAL::Mean_curvature_flow_skeletonization<Polyhedron> Skeletonization;
typedef Skeletonization::Skeleton Skeleton;
typedef Skeleton::vertex_descriptor Skeleton_vertex;
// 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 face_descriptor 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(int argc, char* argv[])
{
std::ifstream input((argc>1)?argv[1]:"data/161.off");
Polyhedron tmesh;
input >> tmesh;
// extract the skeleton
Skeleton skeleton;
CGAL::extract_mean_curvature_flow_skeleton(tmesh, skeleton);
// init the polyhedron simplex indices
CGAL::set_halfedgeds_items_id(tmesh);
//for each input vertex compute its distance to the skeleton
std::vector<double> distances(num_vertices(tmesh));
BOOST_FOREACH(Skeleton_vertex v, vertices(skeleton) )
{
const Point& skel_pt = skeleton[v].point;
BOOST_FOREACH(vertex_descriptor mesh_v, skeleton[v].vertices)
{
const Point& mesh_pt = mesh_v->point();
distances[mesh_v->id()] = std::sqrt(CGAL::squared_distance(skel_pt, mesh_pt));
}
}
// create a property-map for sdf values
std::vector<double> sdf_values( num_faces(tmesh) );
Facet_with_id_pmap<double> sdf_property_map(sdf_values);
// compute sdf values with skeleton
BOOST_FOREACH(face_descriptor f, faces(tmesh))
{
double dist = 0;
BOOST_FOREACH(halfedge_descriptor hd, halfedges_around_face(halfedge(f, tmesh), tmesh))
dist+=distances[target(hd, tmesh)->id()];
sdf_property_map[f] = dist / 3.;
}
// post-process the sdf values
CGAL::sdf_values_postprocessing(tmesh, sdf_property_map);
// create a property-map for segment-ids (it is an adaptor for this case)
std::vector<std::size_t> segment_ids( num_faces(tmesh) );
Facet_with_id_pmap<std::size_t> segment_property_map(segment_ids);
// segment the mesh using default parameters
std::cout << "Number of segments: "
<< CGAL::segmentation_from_sdf_values(tmesh, sdf_property_map, segment_property_map) <<"\n";
return 0;
}