Added a chapter about the navigation on a mesh.

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@231 fdac6126-5c0c-442c-9429-916003d36597

Doc/Examples/nav_code1.cc

@@ -0,0 +1,19 @@
+[...]
+
+TriMesh::HalfedgeHandle heh, heh_init;
+
+// Get the halfedge handle assigned to vertex[0]
+heh = heh_init = mesh.halfedge_handle(vertex[0].handle());
+
+// heh now holds the handle to the initial halfedge.
+// We now get further on the boundary by requesting
+// the next halfedge adjacent to the vertex heh
+// points to...
+heh = mesh.next_halfedge_handle(heh);
+
+// We can do this as often as we want:
+while(heh != heh_init) {
+	heh = mesh.next_halfedge_handle(heh);
+}
+
+[...]

Doc/Examples/nav_code2.cc

@@ -0,0 +1,13 @@
+// Test if a halfedge lies at a boundary (is not adjacent to a face)
+bool is_boundary (HalfedgeHandle _heh) const
+
+// Test if an edge lies at a boundary
+bool is_boundary (EdgeHandle _eh) const
+
+// Test if a vertex is adjacent to a boundary edge
+bool is_boundary (VertexHandle _vh) const
+
+// Test if a face has at least one adjacent boundary edge.
+// If _check_vertex=true, this function also tests if at least one
+// of the adjacent vertices is a boundary vertex
+bool is_boundary (FaceHandle _fh, bool _check_vertex=false) const

Doc/Examples/nav_code3.cc

@@ -0,0 +1,14 @@
+[...]
+
+// Get some vertex handle
+PolyMesh::VertexHandle v = ...;
+
+for(PolyMesh::VertexIHalfedgeIter vih_it = mesh.vih_iter(v); vih_it; ++vih_it) {
+	// Iterate over all incoming halfedges...
+}
+
+for(PolyMesh::VertexOHalfedgeIter voh_it = mesh.voh_iter(v); voh_it; ++voh_it) {
+	// Iterate over all outgoing halfedges...
+}
+
+[...]

Doc/Examples/nav_code4.cc

@@ -0,0 +1,11 @@
+// Get the face adjacent to the opposite halfedge
+OpenMesh::PolyConnectivity::opposite_face_handle();
+
+// Get the handle to the opposite halfedge
+OpenMesh::Concepts::KernelT< FinalMeshItems >::opposite_halfedge_handle();
+
+// Get the opposite vertex to the opposite halfedge
+OpenMesh::TriConnectivity::opposite_he_opposite_vh();
+
+// Get the vertex assigned to the opposite halfedge
+OpenMesh::TriConnectivity::opposite_vh();