code: public double[] getCameraDirection() {
          double[] cameraDirection = new double[3];
          double l = Math.sqrt(Math.pow(this.eyeX - this.centerX, 2.0) + Math.pow(this.eyeZ - this.centerZ, 2.0) + Math.pow(this.eyeZ - this.centerZ, 2.0));
          cameraDirection[0] = (this.centerX - this.eyeX) / l;
          cameraDirection[1] = (this.centerY - this.eyeY) / l;
          cameraDirection[2] = (this.centerZ - this.eyeZ) / l;
          return cameraDirection;
      }
docs: Gets the eye direction of this Camera.
  
  @return
  The eye direction.