Treffer: CHAPTER 6: VR PROGRAMMING.

An authoring environment is an application programming interface-based method of creating a virtual world. A run-time environment subsequently allows the user's real-time interaction with the authored world. For maximum programming flexibility authoring can be done with low-level graphics languages, such as OpenGL. This is a trial-and-error iterative process that require skill and time. The scene graph represents a tree structure, with nodes connected by branches. The topmost node in the hierarchy is the root, which is the parent node to the whole graph.