The term "scene graph" is the by-product of a collision between the fields of discrete mathematics, computer graphics and cinematography. A "scene" in the computer graphics world refers to a collection of objects, their relationship to one another, and a definition of how a viewer sees the objects in the scene. In cinematography, scenes include things like cameras, lights, actors, backgrounds, and so forth.

To most people, a "graph" is something that shows information, such as the performance of the Dow Jones Industrial average over some period of time. However, we're interested in a different type of graph, one from the world of mathematics. The mathematical, or discrete graph, represents a system built from two fundamental entities: nodes and edges. A familiar example of a visual representation of a discrete graph is a family tree. The nodes of the family tree are people, and edges represent the parent-child relationship. This type of graph is a commonly used tool in discrete mathematics, which is the study of states, and transitions from one state to another.

Of all the different types of discrete graphs, the scene graph is a directed, acyclic graph, sometimes called a "tree." There are many specialized properties of this type of graph, illustrated by the directed, acyclic graph of the family tree. Acyclic means that you can't be the parent of your grandfather; there are no loops in the family tree. Directed means that the parent-child relationship is a one-way proposition. The edge between your parent and you represents a special kind of relationship that exists in just one direction.

The scene graph is also a directed, acyclic graph, or tree, consisting of nodes and edges. Elements of the scene that have some data component, such as viewable objects, light sources, camera locations and so forth are contained in the graph nodes. The edges in the scene are like the edges in the family tree, they define not only parent-child relationships, but also, and more importantly, scope of influence of scene parameters.