Quaterniond.rotationTo

Set <code>this</code> quaternion to a rotation that rotates the <code>fromDir</code> vector to point along <code>toDir</code>. <p> Since there can be multiple possible rotations, this method chooses the one with the shortest arc. <p> Reference: <a href="http://stackoverflow.com/questions/1171849/finding-quaternion-representing-the-rotation-from-one-vector-to-another#answer-1171995">stackoverflow.com</a>

@param fromDirX the x-coordinate of the direction to rotate into the destination direction @param fromDirY the y-coordinate of the direction to rotate into the destination direction @param fromDirZ the z-coordinate of the direction to rotate into the destination direction @param toDirX the x-coordinate of the direction to rotate to @param toDirY the y-coordinate of the direction to rotate to @param toDirZ the z-coordinate of the direction to rotate to @return this