mirror of https://github.com/CGAL/cgal
98 lines
2.8 KiB
C++
98 lines
2.8 KiB
C++
#include <CGAL/Simple_cartesian.h>
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#include <CGAL/Polyhedron_3.h>
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#include <iostream>
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#include <list>
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#include <CGAL/boost/graph/kruskal_min_spanning_tree.h>
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typedef CGAL::Simple_cartesian<double> Kernel;
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typedef Kernel::Vector_3 Vector;
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typedef Kernel::Point_3 Point;
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typedef CGAL::Polyhedron_3<Kernel> Polyhedron;
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typedef boost::graph_traits<Polyhedron>::vertex_descriptor vertex_descriptor;
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typedef boost::graph_traits<Polyhedron>::vertex_iterator vertex_iterator;
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typedef boost::graph_traits<Polyhedron>::edge_descriptor edge_descriptor;
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// The BGL makes heavy use of indices associated to the vertices
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// We use a std::map to store the index
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typedef std::map<vertex_descriptor,int> Vertex_index_map;
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Vertex_index_map vertex_index_map;
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// A std::map is not a property map, because it is not lightweight
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typedef boost::associative_property_map<Vertex_index_map> Vertex_index_pmap;
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Vertex_index_pmap vertex_index_pmap(vertex_index_map);
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void
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kruskal(const Polyhedron& P)
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{
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// associate indices to the vertices
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vertex_iterator vb, ve;
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int index = 0;
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// std::tie assigns the first and second element of the std::pair
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// returned by boost::vertices to the variables vb and ve
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for(std::tie(vb, ve)=vertices(P); vb!=ve; ++vb){
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vertex_index_pmap[*vb]= index++;
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}
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// We use the default edge weight which is the length of the edge
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// This property map is defined in graph_traits_Polyhedron_3.h
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// In the function call you can see a named parameter: vertex_index_map
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std::list<edge_descriptor> mst;
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boost::kruskal_minimum_spanning_tree(P,
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std::back_inserter(mst),
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boost::vertex_index_map(vertex_index_pmap));
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std::cout << "#VRML V2.0 utf8\n"
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"Shape {\n"
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" appearance Appearance {\n"
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" material Material { emissiveColor 1 0 0}}\n"
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" geometry\n"
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" IndexedLineSet {\n"
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" coord Coordinate {\n"
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" point [ \n";
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for(std::tie(vb, ve) = vertices(P); vb!=ve; ++vb){
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std::cout << " " << (*vb)->point() << "\n";
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}
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std::cout << " ]\n"
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" }\n"
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" coordIndex [\n";
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for(std::list<edge_descriptor>::iterator it = mst.begin(); it != mst.end(); ++it)
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{
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edge_descriptor e = *it ;
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vertex_descriptor s = source(e,P);
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vertex_descriptor t = target(e,P);
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std::cout << " " << vertex_index_pmap[s] << ", " << vertex_index_pmap[t] << ", -1\n";
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}
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std::cout << "]\n"
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" }#IndexedLineSet\n"
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"}# Shape\n";
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}
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int main() {
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Polyhedron P;
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Point a(1,0,0);
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Point b(0,1,0);
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Point c(0,0,1);
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Point d(0,0,0);
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P.make_tetrahedron(a,b,c,d);
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kruskal(P);
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return 0;
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}
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