CGAL 6.1.1 - Polygon Mesh Processing

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Polygon_mesh_processing/cc_compatible_orientations.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/orientation.h>
#include <CGAL/Polygon_mesh_processing/polygon_soup_to_polygon_mesh.h>
#include <CGAL/Polygon_mesh_processing/stitch_borders.h>
#include <CGAL/IO/polygon_mesh_io.h>
#include <iostream>
#include <string>
#include <cstdlib>
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point;
typedef CGAL::Surface_mesh<Point> Mesh;
namespace PMP = CGAL::Polygon_mesh_processing;
// create a mesh with many connected connected components that should
// be reoriented to define a valid closed mesh
void create_mesh_with_cc_to_orient(Mesh& mesh)
{
const std::string filename = CGAL::data_file_path("meshes/elephant.off");
CGAL::IO::read_polygon_mesh(filename, mesh);
// turn the mesh into a triangle soup, duplicating all the vertices and shuffling orientations
std::vector<Point> points;
std::vector< std::array<std::size_t, 3> > triangles;
triangles.reserve(faces(mesh).size());
points.reserve(3*triangles.size());
for (Mesh::Face_index f : mesh.faces())
{
Mesh::Halfedge_index h = mesh.halfedge(f);
std::size_t s = points.size();
points.push_back(mesh.point(source(h,mesh)));
points.push_back(mesh.point(target(h,mesh)));
points.push_back(mesh.point(target(mesh.next(h),mesh)));
triangles.push_back( {s, s+1, s+2} );
if (std::rand() % 2 == 0)
std::swap(triangles.back()[0], triangles.back()[1]);
}
// load the soup into the mesh;
CGAL::clear(mesh);
PMP::polygon_soup_to_polygon_mesh(points, triangles, mesh);
}
int main()
{
Mesh mesh;
create_mesh_with_cc_to_orient(mesh);
CGAL::IO::write_polygon_mesh("to_orient.off", mesh, CGAL::parameters::stream_precision(17));
// determine face orientations to be reversed to create compatibility
auto fbm = mesh.add_property_map<Mesh::Face_index, bool>("fbm", false).first;
bool is_orientable = PMP::compatible_orientations(mesh, fbm);
assert(is_orientable);
// reverse orientation of faces with bit 1
std::vector<Mesh::Face_index> faces_to_reverse;
for (Mesh::Face_index f : mesh.faces())
if (get(fbm, f))
faces_to_reverse.push_back(f);
PMP::reverse_face_orientations(faces_to_reverse, mesh);
// there are still borders between previously incompatible faces: stitch to close the mesh
PMP::stitch_borders(mesh);
assert(CGAL::is_closed(mesh));
CGAL::IO::write_polygon_mesh("oriented_and_stitched.off", mesh, CGAL::parameters::stream_precision(17));
return 0;
}
CGAL::Exact_predicates_inexact_constructions_kernel
CGAL::Surface_mesh
Kernel::Point_3
CGAL::clear
void clear(FaceGraph &g)
CGAL::is_closed
bool is_closed(const FaceGraph &g)
CGAL::IO::read_polygon_mesh
bool read_polygon_mesh(const std::string &fname, Graph &g, const NamedParameters &np=parameters::default_values())
CGAL::IO::write_polygon_mesh
bool write_polygon_mesh(const std::string &fname, Graph &g, const NamedParameters &np=parameters::default_values())
Kernel