Streams-based animation in an object-oriented graphics environment

Abstract

Animation systems today use a variety of strategies for controlling activity. Some systems employ keyframes, while others use special-purpose scripting languages. Contemporary research systems are developing control through high-level specifications or constraints. This thesis proposes that streams--abstract sequences of values--can serve as a unifying mechanism for control techniques and that various control strategies can be defined as stream generators. A streams-based animation system can incorporate a variety of strategies, providing a flexible environment in which the animator can match control strategy to a particular task.

SWAMP is an object-oriented, streams-based graphics and animation environment. It provides hierarchical object definition, windows, multiple views of objects, and the possibility of multiple renderers. Both textual and mouse-and-menu style interfaces are provided and can be used together. Animation is achieved through attaching streams to objects. Streams are read once each frame, objects are updated, and redisplayed. Stream generators built into SWAMP include keyframes, mouse-based user interaction items, external processes, and rules. These control strategies allow the animator to approach the control task in different ways and from different levels of abstraction. Keyframes and user interaction items give explicit control, external processes provide for algorithmic or procedural control, and rules are a form of declarative control. SWAMP is extensible in that new control strategies, defined as stream generators, are added easily.