1 //=======================================================================
2 // Copyright (c) Aaron Windsor 2007
4 // Distributed under the Boost Software License, Version 1.0. (See
5 // accompanying file LICENSE_1_0.txt or copy at
6 // http://www.boost.org/LICENSE_1_0.txt)
7 //=======================================================================
9 #ifndef __PLANAR_FACE_TRAVERSAL_HPP__
10 #define __PLANAR_FACE_TRAVERSAL_HPP__
15 #include <boost/next_prior.hpp>
16 #include <boost/graph/graph_traits.hpp>
17 #include <boost/graph/properties.hpp>
26 struct planar_face_traversal_visitor
28 void begin_traversal()
34 template <typename Edge>
38 template <typename Vertex>
39 void next_vertex(Vertex)
54 template<typename Graph,
55 typename PlanarEmbedding,
57 typename EdgeIndexMap>
58 void planar_face_traversal(const Graph& g,
59 PlanarEmbedding embedding,
60 Visitor& visitor, EdgeIndexMap em
63 typedef typename graph_traits<Graph>::vertex_descriptor vertex_t;
64 typedef typename graph_traits<Graph>::edge_descriptor edge_t;
65 typedef typename graph_traits<Graph>::vertex_iterator vertex_iterator_t;
66 typedef typename graph_traits<Graph>::edge_iterator edge_iterator_t;
68 property_traits<PlanarEmbedding>::value_type embedding_value_t;
69 typedef typename embedding_value_t::const_iterator embedding_iterator_t;
72 std::vector< std::set<vertex_t> > distinguished_edge_storage_t;
74 std::vector< std::map<vertex_t, edge_t> >
75 distinguished_edge_to_edge_storage_t;
78 boost::iterator_property_map
79 <typename distinguished_edge_storage_t::iterator, EdgeIndexMap>
80 distinguished_edge_map_t;
83 boost::iterator_property_map
84 <typename distinguished_edge_to_edge_storage_t::iterator, EdgeIndexMap>
85 distinguished_edge_to_edge_map_t;
87 distinguished_edge_storage_t visited_vector(num_edges(g));
88 distinguished_edge_to_edge_storage_t next_edge_vector(num_edges(g));
90 distinguished_edge_map_t visited(visited_vector.begin(), em);
91 distinguished_edge_to_edge_map_t next_edge(next_edge_vector.begin(), em);
93 vertex_iterator_t vi, vi_end;
94 typename std::vector<edge_t>::iterator ei, ei_end;
95 edge_iterator_t fi, fi_end;
96 embedding_iterator_t pi, pi_begin, pi_end;
98 visitor.begin_traversal();
100 // Initialize the next_edge property map. This map is initialized from the
101 // PlanarEmbedding so that get(next_edge, e)[v] is the edge that comes
102 // after e in the clockwise embedding around vertex v.
104 for(boost::tie(vi,vi_end) = vertices(g); vi != vi_end; ++vi)
107 pi_begin = embedding[v].begin();
108 pi_end = embedding[v].end();
109 for(pi = pi_begin; pi != pi_end; ++pi)
112 std::map<vertex_t, edge_t> m = get(next_edge, e);
113 m[v] = boost::next(pi) == pi_end ? *pi_begin : *boost::next(pi);
114 put(next_edge, e, m);
118 // Take a copy of the edges in the graph here, since we want to accomodate
119 // face traversals that add edges to the graph (for triangulation, in
120 // particular) and don't want to use invalidated edge iterators.
121 // Also, while iterating over all edges in the graph, we single out
122 // any self-loops, which need some special treatment in the face traversal.
124 std::vector<edge_t> self_loops;
125 std::vector<edge_t> edges_cache;
126 std::vector<vertex_t> vertices_in_edge;
128 for(boost::tie(fi,fi_end) = edges(g); fi != fi_end; ++fi)
131 edges_cache.push_back(e);
132 if (source(e,g) == target(e,g))
133 self_loops.push_back(e);
137 // Iterate over all edges in the graph
138 ei_end = edges_cache.end();
139 for(ei = edges_cache.begin(); ei != ei_end; ++ei)
143 vertices_in_edge.clear();
144 vertices_in_edge.push_back(source(e,g));
145 vertices_in_edge.push_back(target(e,g));
147 typename std::vector<vertex_t>::iterator vi, vi_end;
148 vi_end = vertices_in_edge.end();
150 //Iterate over both vertices in the current edge
151 for(vi = vertices_in_edge.begin(); vi != vi_end; ++vi)
155 std::set<vertex_t> e_visited = get(visited, e);
156 typename std::set<vertex_t>::iterator e_visited_found
159 if (e_visited_found == e_visited.end())
160 visitor.begin_face();
162 while (e_visited.find(v) == e_visited.end())
164 visitor.next_vertex(v);
165 visitor.next_edge(e);
167 put(visited, e, e_visited);
168 v = source(e,g) == v ? target(e,g) : source(e,g);
169 e = get(next_edge, e)[v];
170 e_visited = get(visited, e);
173 if (e_visited_found == e_visited.end())
180 // Iterate over all self-loops, visiting them once separately
181 // (they've already been visited once, this visitation is for
182 // the "inside" of the self-loop)
184 ei_end = self_loops.end();
185 for(ei = self_loops.begin(); ei != ei_end; ++ei)
187 visitor.begin_face();
188 visitor.next_edge(*ei);
189 visitor.next_vertex(source(*ei,g));
193 visitor.end_traversal();
199 template<typename Graph, typename PlanarEmbedding, typename Visitor>
200 inline void planar_face_traversal(const Graph& g,
201 PlanarEmbedding embedding,
205 planar_face_traversal(g, embedding, visitor, get(edge_index, g));
213 #endif //__PLANAR_FACE_TRAVERSAL_HPP__