triangle Intersects Triangle - Java java.lang

Java examples for java.lang:Math Geometry Shape

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Description

triangle Intersects Triangle

Demo Code

/**//w w  w . j  av a 2 s  .  c o  m
 * Java Modular Image Synthesis Toolkit (JMIST)
 * Copyright (C) 2008-2013 Bradley W. Kimmel
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

public class Main{
    public static boolean triangleIntersectsTriangle(Point2 a1, Point2 b1,
            Point2 c1, Point2 a2, Point2 b2, Point2 c2) {

        Point2 p1 = Point2.centroid(a1, b1, c1);
        Point2 p2 = Point2.centroid(a2, b2, c2);
        if (pointInTriangle(p1, a2, b2, c2)
                || pointInTriangle(p2, a1, b1, c1)) {
            return true;
        }

        Ray2[] r1 = { new Ray2(a1, b1), new Ray2(b1, c1), new Ray2(c1, a1) };
        Ray2[] r2 = { new Ray2(a2, b2), new Ray2(b2, c2), new Ray2(c2, a2) };

        for (int i = 0; i < r1.length; i++) {
            for (int j = 0; j < r2.length; j++) {
                if (rayIntersectsRay(r1[i], r2[j])) {
                    return true;
                }
            }
        }

        return false;
    }
    public static boolean pointInTriangle(Point2 p, Point2 a, Point2 b,
            Point2 c) {
        Vector2 ab = a.vectorTo(b);
        Vector2 ac = a.vectorTo(c);
        Vector2 ap = a.vectorTo(p);

        double dot00 = ab.dot(ab);
        double dot01 = ab.dot(ac);
        double dot02 = ab.dot(ap);
        double dot11 = ac.dot(ac);
        double dot12 = ac.dot(ap);

        // Compute barycentric coordinates
        double invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
        double u = (dot11 * dot02 - dot01 * dot12) * invDenom;
        double v = (dot00 * dot12 - dot01 * dot02) * invDenom;

        // Check if point is in triangle
        return (u > 0) && (v > 0) && (u + v < 1);
    }
    public static boolean rayIntersectsRay(Ray2 r1, Ray2 r2) {
        Vector2 r = rayIntersectRay(r1, r2);
        return MathUtil.inRangeOO(r.x, 0.0, r1.limit())
                && MathUtil.inRangeOO(r.y, 0.0, r2.limit());
    }
    public static Vector2 rayIntersectRay(Ray2 r1, Ray2 r2) {
        Vector2 d1 = r1.direction();
        Vector2 d2 = r2.direction();
        LinearMatrix2 T = new LinearMatrix2(d1.x, -d2.x, d1.y, -d2.y);
        Vector2 o12 = r1.origin().vectorTo(r2.origin());

        return T.inverse().times(o12);
    }
}

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