   scengraph, scenemanager?
  what's the difference between a scenegraph and a scenemanager   
  Nothing, both terms refer to the management of objects in your scene.  Scene graph might be a little more specific about how those objects are managed but other than that I don't believe there is a difference.   ;  They're both rather all-encompassing terms that can actually mean a lot of different things based on implementation. "Scene graph" implies something a little more specific and directed than "scene manager;" that's about it.   