/* Auteur: Nicolas JANEY                                */
/* nicolas.janey@univ-fcomte.fr                         */
/* Octobre 2008                                         */
/* Une classe direction en coordonnees homogenes        */

public class Direction3D extends CoordonneesHomogenes3D {

  public Direction3D() {
    super(0.0,0.0,1.0,0.0);
  }

  public Direction3D(double x,double y,double z) {
    super(x,y,z,0.0);
  }

  public Direction3D(Direction3D p) {
    super(p);
  }

  public Direction3D(Position3D pi,
                     Position3D pf) throws ArithmeticException {
    double dx = pf.c[0]-pi.c[0];
    double dy = pf.c[1]-pi.c[1];
    double dz = pf.c[2]-pi.c[2];
    double d = Math.sqrt(dx*dx+dy*dy+dz*dz);
    if ( d == 0.0 ) {
      throw new ArithmeticException(); }
    c = new double[4];
    c[0] = dx/d;
    c[1] = dy/d;
    c[2] = dz/d;
    c[3] = 0.0;
  }
}