text: #include <cstdlib>
  #include <iostream>
  #include <fstream>
  
  #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
  
  #include <CGAL/Random.h>
  #include <CGAL/Surface_mesh.h>
  
  #include <CGAL/Surface_mesh_shortest_path.h>
  
  #include <boost/lexical_cast.hpp>
  
  typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
  typedef CGAL::Surface_mesh<Kernel::Point_3> Triangle_mesh;
  typedef CGAL::Surface_mesh_shortest_path_traits<Kernel, Triangle_mesh> Traits;
  typedef CGAL::Surface_mesh_shortest_path<Traits> Surface_mesh_shortest_path;
  typedef boost::graph_traits<Triangle_mesh> Graph_traits;
  typedef Graph_traits::vertex_iterator vertex_iterator;
  typedef Graph_traits::face_iterator face_iterator;
  
  int main(int argc, char** argv)
  {
    Triangle_mesh tmesh;
    std::ifstream input((argc>1)?argv[1]:"data/elephant.off");
    input >> tmesh;
    input.close();
  
    // pick up a random face
    const unsigned int randSeed = argc > 2 ? boost::lexical_cast<unsigned int>(argv[2]) : 7915421;
    CGAL::Random rand(randSeed);
    const int target_face_index = rand.get_int(0, static_cast<int>(num_faces(tmesh)));
    face_iterator face_it = faces(tmesh).first;
    std::advance(face_it,target_face_index);
    // ... and define a barycentric coordinates inside the face
    Traits::Barycentric_coordinates face_location = {{0.25, 0.5, 0.25}};
  
    // construct a shortest path query object and add a source point
    Surface_mesh_shortest_path shortest_paths(tmesh);
    shortest_paths.add_source_point(*face_it, face_location);
  
    // For all vertices in the tmesh, compute the points of
    // the shortest path to the source point and write them
    // into a file readable using the CGAL Polyhedron demo
    std::ofstream output("shortest_paths_with_id.cgal");
    vertex_iterator vit, vit_end;
    for ( boost::tie(vit, vit_end) = vertices(tmesh);
          vit != vit_end; ++vit)
    {
      std::vector<Traits::Point_3> points;
      shortest_paths.shortest_path_points_to_source_points(*vit, std::back_inserter(points));
  
      // print the points
      output << points.size() << " ";
      for (std::size_t i = 0; i < points.size(); ++i)
        output << " " << points[i];
      output << std::endl;
    }
    return 0;
  }
  