ABSTRACT

Many of the design decisions of virtual environment (VE) applications are driven by the capabilities and limitations of users. These considerations affect both the design of the hardware and the design of the software. To be interactive, a VE software application must constantly present the current view of a computer-generated world and have that world quickly react to the user’s actions. To be convincing, the presentation must provide enough objects and suf˜cient details to make objects easily recognizable to give the user the sense of being in the world. To be useful, the environment must respond to the user. The user’s location in the world should change when a navigation action is performed. Objects that the user can grab or nudge should move as expected. Three-dimensional

11.1 Introduction .......................................................................................................................... 259 11.2 Geometry .............................................................................................................................. 261

11.2.1 Geometric Primitives ................................................................................................ 261 11.2.2 Surfaces ..................................................................................................................... 262 11.2.3 Designing for Rendering Ef˜ciency ..........................................................................264 11.2.4 Scene Graph ..............................................................................................................264 11.2.5 Material Properties ....................................................................................................265 11.2.6 Lighting and Shading ................................................................................................266 11.2.7 Surface Detail ............................................................................................................ 267 11.2.8 Rendering Pipeline ....................................................................................................269