Scripting Interactive Environments with Interval Scripts

In this paper we present a new paradigm for high-level scripting of computer characters and stories in interactive environments called interval scripts. In this paradigm, the actions of characters and users are associated with temporal intervals and scripting is accomplished by establishing temporal constraints between the intervals. Unlike previous constraint-based interaction languages, we employ a strong temporal algebra (based in Allen’s interval algebra) with the ability to express mutually exclusive intervals and to define complex temporal structures. To avoid the typical slowness of strong temporal algebras, we propose a method — PNF propagation — that projects the network implicit in the script into a simpler, 3-valued (past, now, future) network where constraint propagation can be approximately computed in linear time. The paper introduces the interval script paradigm by referring to its current implementation as a text-based language that was used to build three large-scale, computer-vision-based interactive installations. The success on implementing these three very complex projects is presented as evidence that interval scripts are a simpler and more expressive scripting method than any currently used system for scripting interaction in interactiv