Graphics Reference
In-Depth Information
Knowledge of the world
Internal state
Reasoning unit
Sequence of actions
Planner
Strategy
Movement coordinator
Motor activities
DOF manipulator
FIGURE 11.12
Levels of behavior.
Keeping behavior under control
One of the fundamental concerns with autonomous behavior, as with all high-level motion control, is
how to model the behaviors so that they are generated automatically but are still under the control of the
animator. One of the motivations for modeling behaviors is to relieve the animator from specifying the
time-varying values for each of the DOFs of the underlying geometry associated with the object. Pure
autonomy is often not the ultimate goal in designing autonomous agents; often behavior needs to be
controlled in order to be relevant to the objectives of the animator. Also, the control needs to occur at
various levels of specificity.
The various levels of behavior provide hooks with which control over behavior can be exercised.
The animator can insert external control over the behavior by generating imperatives at any of the var-
ious levels: strategies, action sequences, and/or activity invocation. In addition, more general control
can be exercised by setting internal state variables.
Arbitration between competing intentions
As with arbitration among competing forces in flocking, behaviors cannot, in general, be averaged and
expected to produce reasonable results. The highest precedent behavior must be accommodated at all
costs, and other behaviors may be accommodated if they do not contradict the effect of the dominant
behavior. One approach is to group behaviors into sets in which one behavior is selected. Selected
behaviors may then be merged to form the final behavior.
11.3.2 Expressions and gestures
Nothing is more boring than a speaker who stands up and dryly repeats a script without expression,
without a personality. As we have seen in Chapter 10 , there has been a fair amount of work on so-called
talking heads. These are animations where a synthetic face lip-syncs a script. Most of these are cartoon-
like in their lip movement, but they use facial expressions to add interest to the animation.
Several “talking heads” have been created that include facial expressions coordinated with syn-
thetic speech. Greta
[ 31 ] includes wrinkles and furrows to enhance realism. Ruth , the Rutgers
 
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