CGAL 6.2 - Polygon Mesh Processing

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Polygon_mesh_processing/connected_components_example.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/connected_components.h>
#include <CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h>
#include <boost/iterator/function_output_iterator.hpp>
#include <boost/property_map/property_map.hpp>
#include <iostream>
#include <iterator>
#include <map>
#include <string>
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point;
typedef Kernel::Compare_dihedral_angle_3 Compare_dihedral_angle_3;
typedef CGAL::Surface_mesh<Point> Mesh;
namespace PMP = CGAL::Polygon_mesh_processing;
template <typename G>
struct Constraint
{
typedef typename boost::graph_traits<G>::edge_descriptor edge_descriptor;
typedef boost::readable_property_map_tag category;
typedef bool value_type;
typedef bool reference;
typedef edge_descriptor key_type;
Constraint()
:g_(NULL)
{}
Constraint(G& g, double bound)
: g_(&g), bound_(bound)
{}
value_type operator[](edge_descriptor e) const
{
const G& g = *g_;
return compare_(g.point(source(e, g)),
g.point(target(e, g)),
g.point(target(next(halfedge(e, g), g), g)),
g.point(target(next(opposite(halfedge(e, g), g), g), g)),
bound_) == CGAL::SMALLER;
}
friend inline
value_type get(const Constraint& m, const key_type k)
{
return m[k];
}
const G* g_;
Compare_dihedral_angle_3 compare_;
double bound_;
};
template <typename PM>
struct Put_true
{
Put_true(const PM pm)
:pm(pm)
{}
template <typename T>
void operator()(const T& t)
{
put(pm, t, true);
}
PM pm;
};
int main(int argc, char* argv[])
{
const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/blobby_3cc.off");
Mesh mesh;
if(!PMP::IO::read_polygon_mesh(filename, mesh))
{
std::cerr << "Invalid input." << std::endl;
return 1;
}
typedef boost::graph_traits<Mesh>::face_descriptor face_descriptor;
const double bound = std::cos(0.75 * CGAL_PI);
std::vector<face_descriptor> cc;
face_descriptor fd = *faces(mesh).first;
PMP::connected_component(fd,
mesh,
std::back_inserter(cc));
std::cerr << "Connected components without edge constraints" << std::endl;
std::cerr << cc.size() << " faces in the CC of " << fd << std::endl;
// Instead of writing the faces into a container, you can set a face property to true
typedef Mesh::Property_map<face_descriptor, bool> F_select_map;
F_select_map fselect_map =
mesh.add_property_map<face_descriptor, bool>("f:select", false).first;
PMP::connected_component(fd,
mesh,
boost::make_function_output_iterator(Put_true<F_select_map>(fselect_map)));
std::cerr << "\nConnected components with edge constraints (dihedral angle < 3/4 pi)" << std::endl;
Mesh::Property_map<face_descriptor, std::size_t> fccmap =
mesh.add_property_map<face_descriptor, std::size_t>("f:CC").first;
std::size_t num = PMP::connected_components(mesh,
fccmap,
CGAL::parameters::edge_is_constrained_map(Constraint<Mesh>(mesh, bound)));
std::cerr << "- The graph has " << num << " connected components (face connectivity)" << std::endl;
typedef std::map<std::size_t/*index of CC*/, unsigned int/*nb*/> Components_size;
Components_size nb_per_cc;
for(face_descriptor f : faces(mesh)){
nb_per_cc[ fccmap[f] ]++;
}
for(const Components_size::value_type& cc : nb_per_cc){
std::cout << "\t CC #" << cc.first
<< " is made of " << cc.second << " faces" << std::endl;
}
std::cerr << "- We keep only components which have at least 4 faces" << std::endl;
PMP::keep_large_connected_components(mesh,
4,
CGAL::parameters::edge_is_constrained_map(Constraint<Mesh>(mesh, bound)));
std::cerr << "- We keep the two largest components" << std::endl;
PMP::keep_largest_connected_components(mesh,
2,
CGAL::parameters::edge_is_constrained_map(Constraint<Mesh>(mesh, bound)));
return 0;
}
CGAL::Exact_predicates_inexact_constructions_kernel
CGAL::Surface_mesh
Kernel::Point_3
CGAL::Polygon_mesh_processing::connected_components
boost::property_traits< FaceComponentMap >::value_type connected_components(const PolygonMesh &pmesh, FaceComponentMap fcm, const NamedParameters &np=parameters::default_values())
computes for each face the index of the corresponding connected component.
Definition: connected_components.h:199
CGAL::Polygon_mesh_processing::keep_large_connected_components
std::size_t keep_large_connected_components(PolygonMesh &pmesh, const ThresholdValueType threshold_value, const NamedParameters &np=parameters::default_values())
removes connected components whose size is (strictly) smaller than a given threshold value,...
Definition: connected_components.h:537
CGAL::Polygon_mesh_processing::connected_component
FaceOutputIterator connected_component(typename boost::graph_traits< PolygonMesh >::face_descriptor seed_face, const PolygonMesh &pmesh, FaceOutputIterator out, const NamedParameters &np=parameters::default_values())
discovers all the faces in the same connected component as seed_face and records them in out.
Definition: connected_components.h:119
CGAL::Polygon_mesh_processing::keep_largest_connected_components
std::size_t keep_largest_connected_components(PolygonMesh &pmesh, std::size_t nb_components_to_keep, const NamedParameters &np=parameters::default_values())
removes all but a user-defined number of connected components.
Definition: connected_components.h:386
CGAL::SMALLER
SMALLER
Kernel