public Vector3f getDirection(Vector3f store) {
        return rotation.getRotationColumn(2, store);
    }
Retrieves the direction vector the camera is
facing.

@param store storage for the result (modified if not null)
@return the direction the camera is facing.
@see Camera#getDirection()
jme3-core/src/main/java/com/jme3/renderer/Camera.java