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

CGAL 4.8 - Triangulated Surface Mesh Segmentation

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Surface_mesh_segmentation/segmentation_from_sdf_values_SM_example.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/boost/graph/graph_traits_Surface_mesh.h>
#include <CGAL/mesh_segmentation.h>
#include <CGAL/property_map.h>
#include <iostream>
#include <fstream>
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point_3;
typedef CGAL::Surface_mesh<Point_3> Mesh;
typedef boost::graph_traits<Mesh>::vertex_descriptor vertex_descriptor;
typedef boost::graph_traits<Mesh>::face_descriptor face_descriptor;
typedef boost::graph_traits<Mesh>::face_iterator face_iterator;
int main(int argc, char** argv )
{
Mesh mesh;
if (argc==2){
std::ifstream input(argv[1]);
input >> mesh;
} else {
std::ifstream cactus("data/cactus.off");
cactus >> mesh;
}
typedef Mesh::Property_map<face_descriptor,double> Facet_double_map;
Facet_double_map sdf_property_map;
sdf_property_map = mesh.add_property_map<face_descriptor,double>("f:sdf").first;
// compute SDF values
// We can't use default parameters for number of rays, and cone angle
// and the postprocessing
CGAL::sdf_values(mesh, sdf_property_map, 2.0 / 3.0 * CGAL_PI, 25, true);
// create a property-map for segment-ids
typedef Mesh::Property_map<face_descriptor, std::size_t> Facet_int_map;
Facet_int_map segment_property_map = mesh.add_property_map<face_descriptor,std::size_t>("f:sid").first;;
// segment the mesh using default parameters for number of levels, and smoothing lambda
// Any other scalar values can be used instead of using SDF values computed using the CGAL function
std::size_t number_of_segments = CGAL::segmentation_from_sdf_values(mesh, sdf_property_map, segment_property_map);
std::cout << "Number of segments: " << number_of_segments << std::endl;
// print segment-ids
face_iterator facet_it, fend;
BOOST_FOREACH(face_descriptor fd, faces(mesh)){
// ids are between [0, number_of_segments -1]
std::cout << segment_property_map[fd] << " ";
}
std::cout << std::endl;
const std::size_t number_of_clusters = 4; // use 4 clusters in soft clustering
const double smoothing_lambda = 0.3; // importance of surface features, suggested to be in-between [0,1]
// Note that we can use the same SDF values (sdf_property_map) over and over again for segmentation.
// This feature is relevant for segmenting the mesh several times with different parameters.
CGAL::segmentation_from_sdf_values(mesh, sdf_property_map, segment_property_map, number_of_clusters, smoothing_lambda);
}