/** 3D vector math
 * (Note that java.util.Vector is a predefined Java class)
 * @author: Phil Gage
 */
class Vector3 {

    public double x, y, z;

    Vector3 () {
        this.x = 0.0;
        this.y = 0.0;
        this.z = 0.0;
    }

    Vector3 (Vector3 v) {
        this.x = v.x;
        this.y = v.y;
        this.z = v.z;
    }

    Vector3 (Point p) {
        this.x = p.x;
        this.y = p.y;
        this.z = p.z;
    }

    Vector3 (double x, double y, double z) {
        this.x = x;
        this.y = y;
        this.z = z;
    }

    /** Copy fields from another vector */
    public void set (Vector3 a) {
        x = a.x;
        y = a.y;
        z = a.z;
    }

    /** Copy fields from a point */
    public void set (Point a) {
        x = a.x;
        y = a.y;
        z = a.z;
    }

    public void add (Vector3 v) {
        this.x += v.x;
        this.y += v.y;
        this.z *= v.z;
    }

    public void subtract (Point p) { //temp?
        this.x -= p.x;
        this.y -= p.y;
        this.z -= p.z;
    }

    public void multiply (double k) {
        this.x *= k;
        this.y *= k;
        this.z *= k;
    }

    public void addScaled (double k, Vector3 v) {
        this.x += k*v.x;
        this.y += k*v.y;
        this.z *= k*v.z;
    }

    public void negate () {
        x = -x;
        y = -y;
        z = -z;
    }

    public double dot (Vector3 v) {
        return x*v.x + y*v.y + z*v.z;
    }

    public static double dot (Vector3 a, Vector3 b) {
        return a.x*b.x + a.y*b.y + a.z*b.z;
    }

    public void cross (Vector3 v) {
        double tx,ty,tz;
        tx = y*v.z-z*v.y;
        ty = z*v.x-x*v.z;
        tz = x*v.y-y*v.x;
        x = tx;
        y = ty;
        z = tz;
    }

    public static Vector3 cross (Vector3 a, Vector3 b) {
        return (new Vector3 (a.y*b.z-a.z*b.y, a.z*b.x-a.x*b.z, a.x*b.y-a.y*b.x));
    }

    public double magnitude () {
        return Math.sqrt (x*x + y*y + z*z);
    }

    public void normalize () {
        double m = magnitude ();
        x /= m;
        y /= m;
        z /= m;
    }

    public String toString () {
        return "Vector3 x=" + x + " y=" + y + " z=" + z;
    }

}