Calculate the intersection of two lines. - Java java.lang

Java examples for java.lang:Math Geometry Line

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Description

Calculate the intersection of two lines.

Demo Code

// Copyright (C) 2002-2012 Three Rings Design, Inc., All Rights Reserved
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.geom.Point2D;
import static com.threerings.geom.Log.log;

public class Main{
    /**/* w  w w.  j  a va2 s .c  o  m*/
     * Calculate the intersection of two lines. Either line may be considered as a line segment,
     * and the intersecting point is only considered valid if it lies upon the segment.  Note that
     * Point extends Point2D.
     *
     * @param p1 and p2 the coordinates of the first line.
     * @param seg1 if the first line should be considered a segment.
     * @param p3 and p4 the coordinates of the second line.
     * @param seg2 if the second line should be considered a segment.
     * @param result the point that will be filled in with the intersecting point.
     *
     * @return true if result was filled in, or false if the lines are parallel or the point of
     * intersection lies outside of a segment.
     */
    public static boolean lineIntersection(Point2D p1, Point2D p2,
            boolean seg1, Point2D p3, Point2D p4, boolean seg2,
            Point2D result) {
        // see http://astronomy.swin.edu.au/~pbourke/geometry/lineline2d/
        double y43 = p4.getY() - p3.getY();
        double x21 = p2.getX() - p1.getX();
        double x43 = p4.getX() - p3.getX();
        double y21 = p2.getY() - p1.getY();
        double denom = y43 * x21 - x43 * y21;
        if (denom == 0) {
            return false;
        }

        double y13 = p1.getY() - p3.getY();
        double x13 = p1.getX() - p3.getX();
        double ua = (x43 * y13 - y43 * x13) / denom;
        if (seg1 && ((ua < 0) || (ua > 1))) {
            return false;
        }

        if (seg2) {
            double ub = (x21 * y13 - y21 * x13) / denom;
            if ((ub < 0) || (ub > 1)) {
                return false;
            }
        }

        double x = p1.getX() + ua * x21;
        double y = p1.getY() + ua * y21;
        result.setLocation(x, y);
        return true;
    }
}

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