Virtual worlds

Abstract

Virtual worlds, the contents of VR environments, consist of 3D objects with dynamic behavior that react in real time to user input. After a brief overview of the creation process of virtual worlds, this chapter introduces a central data structure of many VR/AR applications, the scene graph, which allows us to structure virtual worlds in a hierarchical manner. Afterwards, different ways to represent 3D objects are presented and discussed in the context of interactive virtual worlds. Special attention is given to methods for optimizing 3D objects with respect to the real-time requirements of virtual worlds. Subsequently, an overview of basic methods for generating the dynamic behavior of 3D objects is given, such as animations, physics-based simulations and the support of user interactions with 3D objects. A section on sound, lighting and backgrounds describes elements of virtual worlds that are supported by common scene graph systems. The concluding section on special-purpose systems deals with 3D objects that are usually modeled with the help of custom methods and tools, such as virtual humans, particle systems, terrains and vegetation.