Barbara Hayes-Roth, Erik Sincoff, Lee Brownston, Ruth Huard, and Brian Lent
Knowledge Systems Laboratory, Stanford University
701 Welch Road, Bldg. A
Palo Alto, California 94305, USA
Telephone: (415) 723-0505
E-Mail: Hayes-Roth@CS.Stanford.Edu, ESincoff@CS.Stanford.Edu,
Brownston@HPP.Stanford.Edu, Huard@Popserver.Stanford.Edu, Lent@CS.Stanford.Edu
Figure 1. Illustrative repertoire of physical behaviors.
Figure 2.Illustrative repertoire of verbal behaviors.
Figure 3.Fully instantiated situated behavior menu.
Situated behavior menus may list fully instantiated behaviors
or abstract classes of behaviors. With instantiated behaviors
(Figure 3), the character immediately executes the child's
selection. Thus the child functions as an improvisational
actor embodied as an animated character. With abstract
behaviors and modifiable moods (Figure 4), the character
improvises a behavior that is consistent with the child's
selection and its current mood. Thus the child functions as an
improvisational director of improvisational actors. Here
children enjoy the combined pleasures of seeing their stories
performed and being surprised by their characters'
improvisations.
Figure 4.Abstract situated behavior menu.
For "Animated Puppets," character empbodiments and their
environment are implemented in a modified version of the
"woggles" animation system developed by Joe Bates at
Carnegie-Mellon University (which also includes the RAL
system of Production Systems Technologies). We have
modified the CMU system so that our characters perform
new physical behaviors, speak lines (conceived and
recorded by Aaron and Nora Hayes-Roth, ages 13 and 10 at
the time), follow directions, and improvise. Thus, the two
systems offer qualitatively different interactive experiences.
In the CMU team's charming "Edge of Intention," users enter
a simulated world of specific woggle individuals (Wolf,
Bear, and Shrimp) in the form of a mouse-controlled user-
woggle. With CAIT's "Animated Puppets," users exercise
artistic expression as creators, directors, and actors of of their
own stories and plays.
Figure 5.System configuration for "Animated Puppets."
Abstract
In "directed improvisation," users give computer characters
abstract directions that establish a skeletal structure for and
other weak constraints on their behavior. The characters
improvise a course of behavior that follows the structure,
meets the constraints, and achieves other application-specific
objectives. Thus, characters perform as directed, but also
surprise and engage users with their improvisations along
the way. In "Animated Puppets," children (or other users)
direct the improvisational behavior of animated characters in
a graphical setting to create their own stories.
Keywords:
Artistic self-expression, Intelligent systems,
Education and entertainment applications, HCI Paradigm
Introduction
We are studying directed improvisation in a Computer-
Animated Improvisational Theater (CAIT), in which children
and animated characters collaborate to create and act out
stories. Children give characters abstract directions that
determine the story's narrative structure. The characters
improvise physical and verbal behaviors that follow the
narrative and meet other performance criteria, e.g., life-like
individual qualities, social conventions, ensemble coherence.
In successive performances of a given story, the characters
improvise different interpretations. CAIT supports several
interaction modes for playcrafting and performance [2]:
animated puppets, animated actors, and several hybrid
modes. This paper describes animated puppets.
CHARACTERS AND BEHAVIOR
Each character has a repertoire of classes and instances of
physical and verbal behaviors to use as building blocks in
improvisations. For example (Figure 1), each character can
go to a designated destination by means of alternative gaits:
bound, jiggle, wobble, beeline, or hop. Similarly (Figure 2),
each character can greet other characters by means of
alternative greeting expressions. Each behavior instance is
annotated with comparative descriptors (e.g., gait speed =
fast, medium, slow). Exploiting these properties, children
and the characters themselves choose different behavior
instances to express emotions or simply to exhibit life-like
behavioral variability. Behavioral idiosyncracies, in their
manner of executing physical behaviors or style of speaking,
allow characters to manifest life-like personalities.
INTERACTING WITH ANIMATED PUPPETS
In animated-puppets mode, children use "situated behavior
menus" to direct characters' improvisations interactively. In
the menu in Figure 3, for example, the character "is
considering" several physical behaviors (go to the pedestal or
the rest area by one of five gaits; or play-alone either of two
games) and verbal behaviors (singing or humming). The
character is capable of performing many other behaviors at
this time, but considers only the subset suggested by its
present situation. For example, it considers only destinations
in its current field of vision. If its gaze should shift, it might
consider other destinations. If another character should
appear, it might consider playing-together as well as playing-
alone. The contents of situated behavior menus change to
track the sets of behaviors characters "are considering."
IIMPLEMENTATION
Children's interactions with animated puppets are mediated
by "intelligent agents" (Figure 5) that interpret directions,
improvise appropriate behavior, and execute that behavior in
their character embodiments. Our architecture is based on the
"dynamic control architecture," implemented as the BB1
system [1]. It allows agents to: (a) continually notice possible
situated behaviors; (b) construct and modify explicit control
plans for their own behavior at run time; and (c) choose to
execute the current situated behavior that best matches the
current control plan. For animated puppets and other modes
of directed improvisation, control plans integrate the
children's directions with the agent's improvised plans.
ONGOING WORK
In ongoing work, we are developing agents that have more
sophisticated improvisational expertise and a new animation
system that lets children create their own characters. We plan
to evaluate our hypothesis that Animated Puppets and other
modes of interaction supported by CAIT will be useful in
teaching children a variety of skills (e.g., problem-solving,
programming concepts, creative writing, social skills) in the
context of an engaging and enjoyable activity.
Acknowledgments
Our agent architecture was developed for a different set of
applications under support from ARPA.
