   Scene Graph, Quadtree, Octtree, and Scene Manager.
  What's the difference between them? I found those on most graphics/game engine.I searched around but still don't get it. Does the Scene Graph, Quadtree and Octtree the same? So what's with the scene manager? Is it the one who manages the Scene Graph, Quadtree, and Octree?   
  Quadtree divides data (or references to data) spatially in 2D. Octree divides data (or references to data) spatially in 3D.The scenegraph is a logical hierachy (tree) that tells something about relationships and connectedness. For instance a house with a table on it with a book on it with a paper clip in it.A Scenegraph makes it easy to let the clip move as the book moves..to let the book and clip fall if the table is crushed etc.Now you can put small scene graphs in octrees and quadtrees..and you can also do it the other way around and make all kinds of hybrids.Now these structures can be used for many things.. I think about it as traversals for different purposes, a rendering traversal a collision traversal a physics update traversal and so on.Scene manager I do not know what it is.;  Hello mrr,Thank you for the very informative post. About the scene graph, I don't really have any idea on how to create one. I made a quadtree for my terrain renderer.. Can I just put it on the scene graph? Is it just a object manager that manages all the objects on the scene? About the scene manager, I just found this one in a graphics engine named Ogre3dThank you very muchJohn Stuart   ;  Scene graphs are used for a couple of things. There was a trend to define the uber scene graph (see e.g. OpenSceneGraph)  before the (IMHO still current) trend to use several, particularly more suited stuctures for the different purposes.mrr has designated a scene graph to build a "logical hierachy". On the other hand, the same post explains forward kinematics due to "parenting" directly from scene graphs. In fact, the latter one is already an interpretation of a scene graph, although a common interpretation. However, there is no real need (and sometimes even no sense) to map the hierachy in a scene graph always to forward kinematics.Octrees are a more specialized structure, namely to query for spatial neighbourhood. E.g. you may attach a bounding volume to each node in a scene graph. The volumes will usually grow the higher the level in the graph is, simply because they follow the hierarchy of the scene graph. So you have a nice containment graph. But collision detection, for example, needs to know about neighbourhood, but not especially containment. So another structure would be better suited for collision detection purposes. One possibility is the said octree.You can find the above conclusion for several other purposes as well. There are articles and blog entries on the internet that mean that the functionality of scene graphs should be "thinned out", using enough additional structures to model the respective purpose as needed.Coming to the term "scene manager". I think there is no common definition of that at all. The term "manager" is used frequently because ... the programmer had no better term at hand (see several threads here on GDnet). So you probably have to investigate the respective sources in the context where you have found it if you want to understand its functionality.   ;  Yes, they can forward kinematics and all kinds of things effects,transformations etc.But I think there is usually some logical connection between the objects even if they move.. a planet orbiting a star.. the wings of a windmill..etc.