A scene graph organizes and controls the rendering of its constituent objects. 3D renderer draws a scene graph in a consistent way that allows for concurrence. 3D renderer can draw one object independently of other objects. 3D can allow such independence because its scene graphs have a particular form and cannot share state among branches of a tree. The hierarchy of the scene graph encourages a natural spatial grouping on the geometric objects found at the leaves of the graph.
Internal nodes act to group their children together.
A group node also defines a spatial bound that contains all the geometry defined by its descendants. Spatial grouping allows for efficient implementation of operations such as proximity detection, collision detection, view frustum culling, and occlusion culling. State Inheritance A leaf node's state is defined by the nodes in a direct path between the scene graph's root and the leaf. 3D renderer can decide to traverse the scene graph in whatever order it wishes. It can traverse the scene graph from left to right and top to bottom, in level order from right to left, or even in parallel.