protected internal virtual void UpdateSceneGraph( Camera camera )
{
// Process queued needUpdate calls
Node.ProcessQueuedUpdates();
// Cascade down the graph updating transforms & world bounds
// In this implementation, just update from the root
// Smarter SceneManager subclasses may choose to update only
// certain scene graph branches based on space partioning info.
this.rootSceneNode.Update( true, false );
}