class SceneGraph
{
public:
	SceneGraph() {
		_rootSceneNode = new SceneNode("RootSceneNode", nullptr);
	}
	~SceneGraph() {
		delete _rootSceneNode;
	}

	//get root SceneNode ptr
	SceneNode* rootSceneNode() { return _rootSceneNode; }

private:
	SceneNode *_rootSceneNode;
};