code: public void set(double x1, double y1, double z1, double w1) {
  		double mag = (1.0/Math.sqrt( x1*x1 + y1*y1 + z1*z1 + w1*w1 ));
  		this.x = x1*mag;
  		this.y = y1*mag;
  		this.z = z1*mag;
  		this.w = w1*mag;
  	}
docs: Set the quaternion coordinates.
  
  @param x1
  @param y1
  @param z1
  @param w1