protected void updateLocalViewDirection() {
        //update local rotation quaternion to use for view rotation
        localForwardRotation.multLocal(rotatedViewDirection.set(viewDirection));
        calculateNewForward(rotation, rotatedViewDirection, localUp);
    }
Updates the local X-Z view direction and the corresponding rotation
quaternion for the spatial.
jme3-jbullet/src/main/java/com/jme3/bullet/control/BetterCharacterControl.java