worldBound.merge(child.getWorldBound());
worldBound = worldBound.merge(child.getWorldBound());
    public void updateWorldBound() {        if(worldBound == null) {            return;        }        boolean foundFirstBound = false;        for (int i = 0; i < children.size(); i++) {            Spatial child = (Spatial) children.get(i);            if (child != null) {                if (foundFirstBound) {                    // merge current world bound with child world bound                    worldBound.merge(child.getWorldBound());                } else {                    // set world bound to first non-null child world bound                    foundFirstBound = true;                    worldBound = child.getWorldBound();                }            }        }    }