Recent work in behavioral animation has taken impressive steps toward autonomous, self-animating
characters for use in production animation and computer games. It remains difficult, however, to direct
autonomous characters to perform specific tasks. To address this problem, we explore the use of cognitive
models. Cognitive models go beyond behavioral models in that they govern what a character knows, how
that knowledge is acquired, and how it can be used to plan actions. To help build cognitive models, we have
developed a cognitive modeling language (CML). Using CML , we can decompose cognitive modeling into
first giving the character domain knowledge, and then specifying the required behavior. The character’s
domain knowledge is specified intuitively in terms of actions, their preconditions and their effects. To
direct the character’s behavior, the animator need only specify a behavior outline, or “sketch plan”, and the
character will automatically work out a sequence of actions that meets the specification. A distinguishing
feature of CML is how we can use familiar control structures to focus the power of the reasoning engine
onto tractable sub-tasks. This forms an important middle ground between regular logic programming and
traditional imperative programming. Moreover, this middle ground allows many behaviors to be specified
more naturally, more simply, more succinctly and at a much higher-level than would otherwise be possible.
In addition, by using interval arithmetic to integrate sensing into our underlying theoretical framework, we
enable characters to generate plans of action even when they find themselves in highly complex, dynamic
virtual worlds. We demonstrate applications of our work to “intelligent” camera control, and behavior
animation for characters situated in a prehistoric world and in a physics-based undersea world.