/* * The JTS Topology Suite is a collection of Java classes that * implement the fundamental operations required to validate a given * geo-spatial data set to a known topological specification. * * Copyright (C) 2001 Vivid Solutions * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * For more information, contact: * * Vivid Solutions * Suite #1A * 2328 Government Street * Victoria BC V8T 5G5 * Canada * * (250)385-6040 * www.vividsolutions.com */ package com.vividsolutions.jts.geomgraph.index; import java.util.*; import com.vividsolutions.jts.geom.*; import com.vividsolutions.jts.geomgraph.*; import com.vividsolutions.jts.algorithm.LineIntersector; import com.vividsolutions.jts.util.Debug; /** * Computes the intersection of line segments, * and adds the intersection to the edges containing the segments. * * @version 1.7 */ public class SegmentIntersector { public static boolean isAdjacentSegments(int i1, int i2) { return Math.abs(i1 - i2) == 1; } /** * These variables keep track of what types of intersections were * found during ALL edges that have been intersected. */ private boolean hasIntersection = false; private boolean hasProper = false; private boolean hasProperInterior = false; // the proper intersection point found private Coordinate properIntersectionPoint = null; private LineIntersector li; private boolean includeProper; private boolean recordIsolated; private boolean isSelfIntersection; //private boolean intersectionFound; private int numIntersections = 0; // testing only public int numTests = 0; private Collection[] bdyNodes; /* public SegmentIntersector() { } */ public SegmentIntersector(LineIntersector li, boolean includeProper, boolean recordIsolated) { this.li = li; this.includeProper = includeProper; this.recordIsolated = recordIsolated; } public void setBoundaryNodes( Collection bdyNodes0, Collection bdyNodes1) { bdyNodes = new Collection[2]; bdyNodes[0] = bdyNodes0; bdyNodes[1] = bdyNodes1; } /** * @return the proper intersection point, or <code>null</code> if none was found */ public Coordinate getProperIntersectionPoint() { return properIntersectionPoint; } public boolean hasIntersection() { return hasIntersection; } /** * A proper intersection is an intersection which is interior to at least two * line segments. Note that a proper intersection is not necessarily * in the interior of the entire Geometry, since another edge may have * an endpoint equal to the intersection, which according to SFS semantics * can result in the point being on the Boundary of the Geometry. */ public boolean hasProperIntersection() { return hasProper; } /** * A proper interior intersection is a proper intersection which is <b>not</b> * contained in the set of boundary nodes set for this SegmentIntersector. */ public boolean hasProperInteriorIntersection() { return hasProperInterior; } /** * A trivial intersection is an apparent self-intersection which in fact * is simply the point shared by adjacent line segments. * Note that closed edges require a special check for the point shared by the beginning * and end segments. */ private boolean isTrivialIntersection(Edge e0, int segIndex0, Edge e1, int segIndex1) { if (e0 == e1) { if (li.getIntersectionNum() == 1) { if (isAdjacentSegments(segIndex0, segIndex1)) return true; if (e0.isClosed()) { int maxSegIndex = e0.getNumPoints() - 1; if ( (segIndex0 == 0 && segIndex1 == maxSegIndex) || (segIndex1 == 0 && segIndex0 == maxSegIndex) ) { return true; } } } } return false; } /** * This method is called by clients of the EdgeIntersector class to test for and add * intersections for two segments of the edges being intersected. * Note that clients (such as MonotoneChainEdges) may choose not to intersect * certain pairs of segments for efficiency reasons. */ public void addIntersections( Edge e0, int segIndex0, Edge e1, int segIndex1 ) { if (e0 == e1 && segIndex0 == segIndex1) return; numTests++; Coordinate p00 = e0.getCoordinates()[segIndex0]; Coordinate p01 = e0.getCoordinates()[segIndex0 + 1]; Coordinate p10 = e1.getCoordinates()[segIndex1]; Coordinate p11 = e1.getCoordinates()[segIndex1 + 1]; li.computeIntersection(p00, p01, p10, p11); //if (li.hasIntersection() && li.isProper()) Debug.println(li); /** * Always record any non-proper intersections. * If includeProper is true, record any proper intersections as well. */ if (li.hasIntersection()) { if (recordIsolated) { e0.setIsolated(false); e1.setIsolated(false); } //intersectionFound = true; numIntersections++; // if the segments are adjacent they have at least one trivial intersection, // the shared endpoint. Don't bother adding it if it is the // only intersection. if (! isTrivialIntersection(e0, segIndex0, e1, segIndex1)) { hasIntersection = true; if (includeProper || ! li.isProper() ) { //Debug.println(li); e0.addIntersections(li, segIndex0, 0); e1.addIntersections(li, segIndex1, 1); } if (li.isProper()) { properIntersectionPoint = (Coordinate) li.getIntersection(0).clone(); hasProper = true; if (! isBoundaryPoint(li, bdyNodes)) hasProperInterior = true; } //if (li.isCollinear()) //hasCollinear = true; } } } private boolean isBoundaryPoint(LineIntersector li, Collection[] bdyNodes) { if (bdyNodes == null) return false; if (isBoundaryPoint(li, bdyNodes[0])) return true; if (isBoundaryPoint(li, bdyNodes[1])) return true; return false; } private boolean isBoundaryPoint(LineIntersector li, Collection bdyNodes) { for (Iterator i = bdyNodes.iterator(); i.hasNext(); ) { Node node = (Node) i.next(); Coordinate pt = node.getCoordinate(); if (li.isIntersection(pt)) return true; } return false; } }