Get the 3D minimum distance between 2 lines vecmath - Java java.lang

Java examples for java.lang:Math Geometry Distance

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Description

Get the 3D minimum distance between 2 lines vecmath

Demo Code


import javax.vecmath.Tuple3d;
import javax.vecmath.Vector3d;

public class Main{
    final static double EPSILON = 0.00000001;
    /**/*from www  .j  a va2s.  c o m*/
     * Get the 3D minimum distance between 2 lines.
     * @see <a href="http://geomalgorithms.com/a07-_distance.html">Distance</a>
     *
     * @param L1 3D lines
     * @param L2 3D lines
     * @return the shortest distance between L1 and L2
     */
    public static double distance(LinePoints3d L1, LinePoints3d L2) {

        Vector3d u = sub(L1.getP2(), L1.getP1());
        Vector3d v = sub(L2.getP2(), L2.getP1());
        Vector3d w = sub(L1.getP1(), L2.getP1());

        // always >= 0
        double a = dot(u, u);
        double b = dot(u, v);

        // always >= 0
        double c = dot(v, v);
        double d = dot(u, w);
        double e = dot(v, w);

        // always >= 0
        double D = a * c - b * b;
        double sc, tc;

        // compute the line parameters of the two closest points
        if (D < EPSILON) {
            // the lines are almost parallel
            sc = 0.0;
            // use the largest denominator
            tc = (b > c ? d / b : e / c);
        } else {
            sc = (b * e - c * d) / D;
            tc = (a * e - b * d) / D;
        }

        // get the difference of the two closest points
        // dP = L1(sc) - L2(tc)
        // dP = w + (sc * u) - (tc * v)

        u.scale(sc);
        v.scale(tc);

        Vector3d dP = w;
        dP.add(u);
        dP.sub(v);

        // return the closest distance
        return dP.length();
    }
    static Vector3d sub(Tuple3d t0, Tuple3d t1) {
        return new Vector3d(t0.x - t1.x, t0.y - t1.y, t0.z - t0.z);
    }
    static double dot(Tuple3d v0, Tuple3d v1) {
        return (v0.x * v1.x + v0.y * v1.y + v0.z * v1.z);
    }
}

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