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#include <CGAL/Simple_cartesian.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/boost/graph/graph_traits_Surface_mesh.h>
#include <CGAL/boost/graph/properties_Surface_mesh.h>
#include <CGAL/Mean_curvature_flow_skeletonization.h>
#include <fstream>
typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_3 Point;
typedef CGAL::Surface_mesh<Point> Triangle_mesh;
typedef boost::graph_traits<Triangle_mesh>::vertex_descriptor vertex_descriptor;
typedef CGAL::Mean_curvature_flow_skeletonization<Triangle_mesh> Skeletonization;
typedef Skeletonization::Skeleton Skeleton;
typedef Skeleton::vertex_descriptor Skeleton_vertex;
typedef Skeleton::edge_descriptor Skeleton_edge;
int main(int argc, char* argv[])
{
std::ifstream input((argc>1)?argv[1]:"data/elephant.off");
Triangle_mesh tmesh;
input >> tmesh;
Skeleton skeleton;
Skeletonization mcs(tmesh);
// 1. Contract the mesh by mean curvature flow.
mcs.contract_geometry();
// 2. Collapse short edges and split bad triangles.
mcs.collapse_edges();
mcs.split_faces();
// 3. Fix degenerate vertices.
mcs.detect_degeneracies();
// Perform the above three steps in one iteration.
mcs.contract();
// Iteratively apply step 1 to 3 until convergence.
mcs.contract_until_convergence();
// Convert the contracted mesh into a curve skeleton and
// get the correspondent surface points
mcs.convert_to_skeleton(skeleton);
std::cout << "Number of vertices of the skeleton: " << boost::num_vertices(skeleton) << "\n";
std::cout << "Number of edges of the skeleton: " << boost::num_edges(skeleton) << "\n";
// Output all the edges of the skeleton.
std::ofstream output("skel.cgal");
BOOST_FOREACH(Skeleton_edge e, edges(skeleton))
{
const Point& s = skeleton[source(e, skeleton)].point;
const Point& t = skeleton[target(e, skeleton)].point;
output << "2 "<< s << " " << t << "\n";
}
output.close();
// Output skeleton points and the corresponding surface points
output.open("correspondance.cgal");
BOOST_FOREACH(Skeleton_vertex v, vertices(skeleton))
BOOST_FOREACH(vertex_descriptor vd, skeleton[v].vertices)
output << "2 " << skeleton[v].point << " " << get(CGAL::vertex_point, tmesh, vd) << "\n";
return 0;
}
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