private void checkActiveChild(Vector3f vector3f) {
            AppStateManager stateManager = application.getStateManager();
            if(vector3f == null){
                if(currentActiveChild != null){
                    logger.log(Level.INFO, "Detach child {0}", currentActiveChild);
                    stateManager.detach(currentActiveChild);
                    currentActiveChild = null;
                }
                return;
            }
            if (currentActiveChild == null) {
                currentActiveChild = new InceptionLevel(this, vector3f);
                stateManager.attach(currentActiveChild);
                logger.log(Level.INFO, "Attach child {0}", currentActiveChild);
            } else if (!currentActiveChild.getPositionInParent().equals(vector3f)) {
                logger.log(Level.INFO, "Switching from child {0}", currentActiveChild);
                stateManager.detach(currentActiveChild);
                currentActiveChild = new InceptionLevel(this, vector3f);
                stateManager.attach(currentActiveChild);
                logger.log(Level.INFO, "Attach child {0}", currentActiveChild);
            }
        }
WorldOfInception - Find the galaxy center ;)

@author normenhansen
jme3-examples/src/main/java/jme3test/games/WorldOfInception.java