/*
* 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.revolsys.geometry.algorithm;
import com.revolsys.geometry.model.BoundingBox;
import com.revolsys.geometry.model.Point;
import com.revolsys.geometry.model.coordinates.CentralEndpointIntersector;
import com.revolsys.geometry.model.coordinates.CoordinatesUtil;
import com.revolsys.geometry.model.coordinates.LineSegmentUtil;
import com.revolsys.geometry.model.impl.BoundingBoxDoubleXY;
import com.revolsys.geometry.model.impl.PointDoubleXY;
import com.revolsys.geometry.util.BoundingBoxUtil;
/**
* A robust version of {@link LineIntersector}.
*
* @version 1.7
* @see RobustDeterminant
*/
public class RobustLineIntersector extends LineIntersector {
public RobustLineIntersector() {
}
public RobustLineIntersector(final double scale) {
super(scale);
}
private int computeCollinearIntersection(final double line1x1, final double line1y1,
final double line1x2, final double line1y2, final double line2x1, final double line2y1,
final double line2x2, final double line2y2) {
final boolean p1q1p2 = BoundingBoxUtil.intersects(line1x1, line1y1, line1x2, line1y2, line2x1,
line2y1);
final boolean p1q2p2 = BoundingBoxUtil.intersects(line1x1, line1y1, line1x2, line1y2, line2x2,
line2y2);
final boolean q1p1q2 = BoundingBoxUtil.intersects(line2x1, line2y1, line2x2, line2y2, line1x1,
line1y1);
final boolean q1p2q2 = BoundingBoxUtil.intersects(line2x1, line2y1, line2x2, line2y2, line1x2,
line1y2);
if (p1q1p2 && p1q2p2) {
this.intersectionX1 = line2x1;
this.intersectionY1 = line2y1;
this.intersectionX2 = line2x2;
this.intersectionY2 = line2y2;
return COLLINEAR_INTERSECTION;
} else if (q1p1q2 && q1p2q2) {
this.intersectionX1 = line1x1;
this.intersectionY1 = line1y1;
this.intersectionX2 = line1x2;
this.intersectionY2 = line1y2;
return COLLINEAR_INTERSECTION;
} else if (p1q1p2 && q1p1q2) {
this.intersectionX1 = line2x1;
this.intersectionY1 = line2y1;
if (line2x1 == line1x1 && line2y1 == line1y1 && !p1q2p2 && !q1p2q2) {
return POINT_INTERSECTION;
} else {
this.intersectionX2 = line1x1;
this.intersectionY2 = line1y1;
return COLLINEAR_INTERSECTION;
}
} else if (p1q1p2 && q1p2q2) {
this.intersectionX1 = line2x1;
this.intersectionY1 = line2y1;
if (line2x1 == line1x2 && line2y1 == line1y2 && !p1q2p2 && !q1p1q2) {
return POINT_INTERSECTION;
} else {
this.intersectionX2 = line1x2;
this.intersectionY2 = line1y2;
return COLLINEAR_INTERSECTION;
}
} else if (p1q2p2 && q1p1q2) {
this.intersectionX1 = line2x2;
this.intersectionY1 = line2y2;
if (line2x2 == line1x1 && line2y2 == line1y1 && !p1q1p2 && !q1p2q2) {
return POINT_INTERSECTION;
} else {
this.intersectionX2 = line1x1;
this.intersectionY2 = line1y1;
return COLLINEAR_INTERSECTION;
}
} else if (p1q2p2 && q1p2q2) {
this.intersectionX1 = line2x2;
this.intersectionY1 = line2y2;
if (line2x2 == line1x2 && line2y2 == line1y2 && !p1q1p2 && !q1p1q2) {
return POINT_INTERSECTION;
} else {
this.intersectionX2 = line1x2;
this.intersectionY2 = line1y2;
return COLLINEAR_INTERSECTION;
}
} else {
return NO_INTERSECTION;
}
}
@Override
protected int computeIntersect(final double line1x1, final double line1y1, final double line1x2,
final double line1y2, final double line2x1, final double line2y1, final double line2x2,
final double line2y2) {
this.isProper = false;
// first try a fast test to see if the envelopes of the lines intersect
if (!BoundingBoxUtil.intersectsMinMax(line1x1, line1y1, line1x2, line1y2, line2x1, line2y1,
line2x2, line2y2)) {
return NO_INTERSECTION;
}
// for each endpoint, compute which side of the other segment it lies
// if both endpoints lie on the same side of the other segment,
// the segments do not intersect
final int Pq1 = CGAlgorithmsDD.orientationIndex(line1x1, line1y1, line1x2, line1y2, line2x1,
line2y1);
final int Pq2 = CGAlgorithmsDD.orientationIndex(line1x1, line1y1, line1x2, line1y2, line2x2,
line2y2);
if (Pq1 > 0 && Pq2 > 0 || Pq1 < 0 && Pq2 < 0) {
return NO_INTERSECTION;
}
final int Qp1 = CGAlgorithmsDD.orientationIndex(line2x1, line2y1, line2x2, line2y2, line1x1,
line1y1);
final int Qp2 = CGAlgorithmsDD.orientationIndex(line2x1, line2y1, line2x2, line2y2, line1x2,
line1y2);
if (Qp1 > 0 && Qp2 > 0 || Qp1 < 0 && Qp2 < 0) {
return NO_INTERSECTION;
}
final boolean collinear = Pq1 == 0 && Pq2 == 0 && Qp1 == 0 && Qp2 == 0;
if (collinear) {
return computeCollinearIntersection(line1x1, line1y1, line1x2, line1y2, line2x1, line2y1,
line2x2, line2y2);
}
/**
* At this point we know that there is a single intersection point
* (since the lines are not collinear).
*/
/**
* Check if the intersection is an endpoint. If it is, copy the endpoint as
* the intersection point. Copying the point rather than computing it
* ensures the point has the exact value, which is important for
* robustness. It is sufficient to simply check for an endpoint which is on
* the other line, since at this point we know that the inputLines must
* intersect.
*/
if (Pq1 == 0 || Pq2 == 0 || Qp1 == 0 || Qp2 == 0) {
this.isProper = false;
/**
* Check for two equal endpoints.
* This is done explicitly rather than by the orientation tests
* below in order to improve robustness.
*
* [An example where the orientation tests fail to be consistent is
* the following (where the true intersection is at the shared endpoint
* POINT (19.850257749638203 46.29709338043669)
*
* LINESTRING ( 19.850257749638203 46.29709338043669, 20.31970698357233 46.76654261437082 )
* and
* LINESTRING ( -48.51001596420236 -22.063180333403878, 19.850257749638203 46.29709338043669 )
*
* which used to produce the INCORRECT result: (20.31970698357233, 46.76654261437082, NaN)
*
*/
if (line1x1 == line2x1 && line1y1 == line2y1 || line1x1 == line2x2 && line1y1 == line2y2) {
this.intersectionX1 = line1x1;
this.intersectionY1 = line1y1;
} else if (line1x2 == line2x1 && line1y2 == line2y1
|| line1x2 == line2x2 && line1y2 == line2y2) {
this.intersectionX1 = line1x2;
this.intersectionY1 = line1y2;
} else if (Pq1 == 0) {
/**
* Now check to see if any endpoint lies on the interior of the other segment.
*/
this.intersectionX1 = line2x1;
this.intersectionY1 = line2y1;
} else if (Pq2 == 0) {
this.intersectionX1 = line2x2;
this.intersectionY1 = line2y2;
} else if (Qp1 == 0) {
this.intersectionX1 = line1x1;
this.intersectionY1 = line1y1;
} else if (Qp2 == 0) {
this.intersectionX1 = line1x2;
this.intersectionY1 = line1y2;
}
} else {
this.isProper = true;
final Point intersectionPoint = intersection(line1x1, line1y1, line1x2, line1y2, line2x1,
line2y1, line2x2, line2y2);
this.intersectionX1 = intersectionPoint.getX();
this.intersectionY1 = intersectionPoint.getY();
}
return POINT_INTERSECTION;
}
@Override
public boolean computeIntersection(final double x, final double y, final double x1,
final double y1, final double x2, final double y2) {
this.isProper = false;
// do between check first, since it is faster than the orientation test
if (BoundingBoxUtil.intersects(x1, y1, x2, y2, x, y)) {
if (CGAlgorithmsDD.orientationIndex(x1, y1, x2, y2, x, y) == 0
&& CGAlgorithmsDD.orientationIndex(x2, y2, x1, y1, x, y) == 0) {
this.isProper = true;
if (x == x1 && y == y1 || x == x2 && y == y2) {
this.isProper = false;
}
this.intersectionCount = POINT_INTERSECTION;
return true;
}
}
this.intersectionCount = NO_INTERSECTION;
return false;
}
/**
* This method computes the actual value of the intersection point.
* To obtain the maximum precision from the intersection calculation,
* the coordinates are normalized by subtracting the minimum
* ordinate values (in absolute value). This has the effect of
* removing common significant digits from the calculation to
* maintain more bits of precision.
*/
private Point intersection(final double line1x1, final double line1y1, final double line1x2,
final double line1y2, final double line2x1, final double line2y1, final double line2x2,
final double line2y2) {
Point intPt = intersectionWithNormalization(line1x1, line1y1, line1x2, line1y2, line2x1,
line2y1, line2x2, line2y2);
/*
* // TESTING ONLY Point intPtDD = CGAlgorithmsDD.intersection(p1, p2, q1, q2); double dist =
* intPt.distance(intPtDD); System.out.println(intPt + " - " + intPtDD + " dist = " + dist);
* //intPt = intPtDD;
*/
/**
* Due to rounding it can happen that the computed intersection is
* outside the envelopes of the input segments. Clearly this
* is inconsistent.
* This code checks this condition and forces a more reasonable answer
*
* MD - May 4 2005 - This is still a problem. Here is a failure case:
*
* LINESTRING (2089426.5233462777 1180182.3877339689, 2085646.6891757075 1195618.7333999649)
* LINESTRING (1889281.8148903656 1997547.0560044837, 2259977.3672235999 483675.17050843034)
* int point = (2097408.2633752143,1144595.8008114607)
*
* MD - Dec 14 2006 - This does not seem to be a failure case any longer
*/
if (!isInSegmentEnvelopes(intPt)) {
intPt = nearestEndpoint(line1x1, line1y1, line1x2, line1y2, line2x1, line2y1, line2x2,
line2y2);
}
return CoordinatesUtil.getPrecise(this.scale, intPt);
}
private Point intersectionWithNormalization(final double line1x1, final double line1y1,
final double line1x2, final double line1y2, final double line2x1, final double line2y1,
final double line2x2, final double line2y2) {
final double minX0 = line1x1 < line1x2 ? line1x1 : line1x2;
final double minY0 = line1y1 < line1y2 ? line1y1 : line1y2;
final double maxX0 = line1x1 > line1x2 ? line1x1 : line1x2;
final double maxY0 = line1y1 > line1y2 ? line1y1 : line1y2;
final double minX1 = line2x1 < line2x2 ? line2x1 : line2x2;
final double minY1 = line2y1 < line2y2 ? line2y1 : line2y2;
final double maxX1 = line2x1 > line2x2 ? line2x1 : line2x2;
final double maxY1 = line2y1 > line2y2 ? line2y1 : line2y2;
final double intMinX = minX0 > minX1 ? minX0 : minX1;
final double intMaxX = maxX0 < maxX1 ? maxX0 : maxX1;
final double intMinY = minY0 > minY1 ? minY0 : minY1;
final double intMaxY = maxY0 < maxY1 ? maxY0 : maxY1;
final double normX = (intMinX + intMaxX) / 2.0;
final double normY = (intMinY + intMaxY) / 2.0;
final Point intPt = safeHCoordinatesIntersection(//
line1x1 - normX, line1y1 - normY, //
line1x2 - normX, line1y2 - normY, //
line2x1 - normX, line2y1 - normY, //
line2x2 - normX, line2y2 - normY);
final double x = intPt.getX() + normX;
final double y = intPt.getY() + normY;
return new PointDoubleXY(x, y);
}
/**
* Tests whether a point lies in the envelopes of both input segments.
* A correctly computed intersection point should return <code>true</code>
* for this test.
* Since this test is for debugging purposes only, no attempt is
* made to optimize the envelope test.
*
* @return <code>true</code> if the input point lies within both input segment envelopes
*/
private boolean isInSegmentEnvelopes(final Point intPt) {
final BoundingBox env0 = BoundingBoxDoubleXY.newBoundingBoxDoubleXY(this.line1x1, this.line1y1,
this.line1x2, this.line1y2);
final BoundingBox env1 = BoundingBoxDoubleXY.newBoundingBoxDoubleXY(this.line2x1, this.line2y1,
this.line2x2, this.line2y2);
return env0.covers(intPt) && env1.covers(intPt);
}
/**
* Finds the endpoint of the segments P and Q which
* is closest to the other segment.
* This is a reasonable surrogate for the true
* intersection points in ill-conditioned cases
* (e.g. where two segments are nearly coincident,
* or where the endpoint of one segment lies almost on the other segment).
* <p>
* This replaces the older CentralEndpoint heuristic,
* which chose the wrong endpoint in some cases
* where the segments had very distinct slopes
* and one endpoint lay almost on the other segment.
*
* @param p1 an endpoint of segment P
* @param p2 an endpoint of segment P
* @param q1 an endpoint of segment Q
* @param q2 an endpoint of segment Q
* @return the nearest endpoint to the other segment
*/
private Point nearestEndpoint(final double line1x1, final double line1y1, final double line1x2,
final double line1y2, final double line2x1, final double line2y1, final double line2x2,
final double line2y2) {
double x = line1x1;
double y = line1y1;
double minDist = LineSegmentUtil.distanceLinePoint(line2x1, line2y1, line2x2, line2y2, line1x1,
line1y1);
double dist = LineSegmentUtil.distanceLinePoint(line2x1, line2y1, line2x2, line2y2, line1x2,
line1y2);
if (dist < minDist) {
minDist = dist;
x = line1x2;
y = line1y2;
}
dist = LineSegmentUtil.distanceLinePoint(line1x1, line1y1, line1x2, line1y2, line2x1, line2y1);
if (dist < minDist) {
minDist = dist;
x = line2x1;
y = line2y1;
}
dist = LineSegmentUtil.distanceLinePoint(line1x1, line1y1, line1x2, line1y2, line2x2, line2y2);
if (dist < minDist) {
minDist = dist;
x = line2x2;
y = line2y2;
}
return new PointDoubleXY(x, y);
}
/**
* Computes a segment intersection using homogeneous coordinates. Round-off
* error can cause the raw computation to fail, (usually due to the segments
* being approximately parallel). If this happens, a reasonable approximation
* is computed instead.
*
* @param p1 a segment endpoint
* @param p2 a segment endpoint
* @param q1 a segment endpoint
* @param q2 a segment endpoint
* @return the computed intersection point
*/
private Point safeHCoordinatesIntersection(final double line1x1, final double line1y1,
final double line1x2, final double line1y2, final double line2x1, final double line2y1,
final double line2x2, final double line2y2) {
Point intersectionPoint;
try {
intersectionPoint = HCoordinate.intersection(line1x1, line1y1, line1x2, line1y2, line2x1,
line2y1, line2x2, line2y2);
} catch (final NotRepresentableException e) {
// compute an approximate result
intersectionPoint = CentralEndpointIntersector.getIntersection(line1x1, line1y1, line1x2,
line1y2, line2x1, line2y1, line2x2, line2y2);
}
return intersectionPoint;
}
}