/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2001-2006 Vivid Solutions
* (C) 2001-2008, Open Source Geospatial Foundation (OSGeo)
*
* 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;
* version 2.1 of the License.
*
* 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.
*/
package org.geotools.geometry.iso.topograph2D.index;
import java.util.Collection;
import java.util.Iterator;
import org.geotools.geometry.iso.topograph2D.Coordinate;
import org.geotools.geometry.iso.topograph2D.Edge;
import org.geotools.geometry.iso.topograph2D.Node;
import org.geotools.geometry.iso.util.algorithm2D.LineIntersector;
/**
* Keeps informations about the intersections of Segments.
* Uses a LineIntersector to calculate the intersection between two line segments.
*
*
*
* @source $URL$
*/
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;
}
}