The computation of the IntersectionMatrix relies on the use of a structure called a "topology graph". The topology graph contains nodes and edges corresponding to the nodes and line segments of a Geometry. Each node and edge in the graph is labeled with its topological location relative to the source geometry.

Note that there is no requirement that points of self-intersection be a vertex. Thus to obtain a correct topology graph, Geometrys must be self-noded before constructing their graphs.

Two fundamental operations are supported by topology graphs:

Computing the intersections between all the edges and nodes of a single graph
Computing the intersections between the edges and nodes of two different graphs

Other

version: 1.7

public PlanarGraph(NodeFactory nodeFact)

public PlanarGraph()

public static void linkResultDirectedEdges(Collection nodes)

For nodes in the Collection, link the DirectedEdges at the node that are in the result. This allows clients to link only a subset of nodes in the graph, for efficiency (because they know that only a subset is of interest).

public Iterator getEdgeIterator()

public Collection getEdgeEnds()

public boolean isBoundaryNode(int geomIndex, Coordinate coord)

protected void insertEdge(Edge e)

public void add(EdgeEnd e)

public Iterator getNodeIterator()

public Collection getNodes()

public Node addNode(Node node)

public Node addNode(Coordinate coord)

public Node find(Coordinate coord)

Returns:: the node if found; null otherwise

public void addEdges(List edgesToAdd)

Add a set of edges to the graph. For each edge two DirectedEdges will be created. DirectedEdges are NOT linked by this method.

public void linkResultDirectedEdges()

Link the DirectedEdges at the nodes of the graph. This allows clients to link only a subset of nodes in the graph, for efficiency (because they know that only a subset is of interest).

public void linkAllDirectedEdges()

Link the DirectedEdges at the nodes of the graph. This allows clients to link only a subset of nodes in the graph, for efficiency (because they know that only a subset is of interest).

public EdgeEnd findEdgeEnd(Edge e)

Returns the EdgeEnd which has edge e as its base edge (MD 18 Feb 2002 - this should return a pair of edges)

Returns:: the edge, if found null if the edge was not found

public Edge findEdge(Coordinate p0, Coordinate p1)

Returns the edge whose first two coordinates are p0 and p1

Returns:: the edge, if found null if the edge was not found

public Edge findEdgeInSameDirection(Coordinate p0, Coordinate p1)

Returns the edge which starts at p0 and whose first segment is parallel to p1

Returns:: the edge, if found null if the edge was not found

public void printEdges(PrintStream out)