Class SimpleEdgeSetIntersector

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4	/*
5	* Copyright (c) 2016 Vivid Solutions.
6	*
7	* All rights reserved. This program and the accompanying materials
8	* are made available under the terms of the Eclipse Public License 2.0
9	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
10	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
11	* and the Eclipse Distribution License is available at
12	*
13	* http://www.eclipse.org/org/documents/edl-v10.php.
14	*/
15	package org.locationtech.jts.geomgraph.index;
16
17	import java.util.Iterator;
18	import java.util.List;
19
20	import org.locationtech.jts.geom.Coordinate;
21	import org.locationtech.jts.geomgraph.Edge;
22
23	/**
24	* Finds all intersections in one or two sets of edges,
25	* using the straightforward method of
26	* comparing all segments.
27	* This algorithm is too slow for production use, but is useful for testing purposes.
28	* @version 1.7
29	*/
30	public class SimpleEdgeSetIntersector
31	extends EdgeSetIntersector
32	{
33	// statistics information
34	int nOverlaps;
35
36	public SimpleEdgeSetIntersector() {
37	}
38
39	public void computeIntersections(List edges, SegmentIntersector si, boolean testAllSegments)
40	{
41	nOverlaps = 0;
42
43	for (Iterator i0 = edges.iterator(); i0.hasNext(); ) {
44	Edge edge0 = (Edge) i0.next();
45	for (Iterator i1 = edges.iterator(); i1.hasNext(); ) {
46	Edge edge1 = (Edge) i1.next();
47	if (testAllSegments \|\| edge0 != edge1)
48	computeIntersects(edge0, edge1, si);
49	}
50	}
51	}
52
53
54	public void computeIntersections(List edges0, List edges1, SegmentIntersector si)
55	{
56	nOverlaps = 0;
57
58	for (Iterator i0 = edges0.iterator(); i0.hasNext(); ) {
59	Edge edge0 = (Edge) i0.next();
60	for (Iterator i1 = edges1.iterator(); i1.hasNext(); ) {
61	Edge edge1 = (Edge) i1.next();
62	computeIntersects(edge0, edge1, si);
63	}
64	}
65	}
66
67	/**
68	* Performs a brute-force comparison of every segment in each Edge.
69	* This has n^2 performance, and is about 100 times slower than using
70	* monotone chains.
71	*/
72	private void computeIntersects(Edge e0, Edge e1, SegmentIntersector si)
73	{
74	Coordinate[] pts0 = e0.getCoordinates();
75	Coordinate[] pts1 = e1.getCoordinates();
76	for (int i0 = 0; i0 < pts0.length - 1; i0++) {
77	for (int i1 = 0; i1 < pts1.length - 1; i1++) {
78	si.addIntersections(e0, i0, e1, i1);
79	}
80	}
81	}
82	}
83