Biomedical Engineering Reference
In-Depth Information
games, the correspondent computational process-
ing is known simply as
pathinding
, and in some
cases is the main AI implemented.
Frequently, when a character is trying to satisfy
a goal
,
finding the path to a certain location is not
the only choice to be made. For instance, maybe
it should be better to run rather than simply to
walk. Sometimes, to reach the goal it is neces-
sary to jump or to climb something. Of course,
it depends on which are the possible movements
available to the character. Besides, it has to be
reminded that each one of them has to match a
different animation sequence. Usually based on
graphs of positions and paths on the map, path-
finding may also include some knowledge about
the environment that is necessary for choosing
where to go to solve the current problem when
the solution is not immediately available. Since
this level of computation involves some kind of
decision-making process, it may sometimes be
rather complex. If the character faces a rich en-
vironment with many different possible solutions,
some heuristics may be required.
Until this point, only simple and basic be-
haviors have been considered, those that can
be described as
body movements
. They are ex-
ecuted through computer animation techniques
controlled by basic AI algorithms of pathfinding
and decision-making processing. Although far
from complete, frequently they are responsible
for all the character behavior implemented in
many VEs, especially when computer games
are considered. In fact, body movements are the
minimum expected behavior performed by a
character that has to look alive. Body expression
and apparently intentional displacements are per-
haps the minimum an observer needs to believe
that there is a “living” entity present in a virtual
environment. Despite their apparent simplicity,
they may represent considerable real-time, com-
plex computational processing, especially in large
and very populated virtual environments. Perhaps
for commercial reasons, the graphical aspects
of character body movements are frequently the
main concern regarding character believability.
Altogether, these computational processes don't
leave much resource for implementing more
sophisticated behaviors. However, for many ap-
plications it may be important to have characters
exhibiting more complex and adaptive behavior
while still preserving an interesting appearance.
Then, there has to be a character behavior structure
including a flexible and context-sensitive action
selection mechanism that doesn't consume too
much computational resource. Such a process
should then be responsible for the lower-level
control of decision-making, path finding, and
body expression and movements.
behavior as Action Selection
Human observers evaluate characters believability
not only by how they look. Their sequences of
actions have to be consistent and reveal goal-ori-
ented behaviors that look as if they are attempting
to satisfy internal needs. Also, awareness of the
possibilities and obstacles of the environment has
to be expressed. Some kind of “internal life” has
to be emulated. That is the way a character may
seem intelligent and emotional.
Franklin (1995) has postulated the Action Se-
lection Paradigm, by which the prevailing task of
the mind is to bring about the next action. Actions
serve internal drives and are controlled by the
mind in situated autonomous agents. All cogni-
tive functions (sensing, recognizing, reasoning,
planning, etc.) are subordinated to mind control
to produce a consistent action flow, coherent with
the dynamic internal states of an agent and the
current environment possibilities.
So, we can think of a character artificial mind
as a central control that integrates and coordinates
all cognitive functions in order to select actions
that serve internal forces in its interaction with
the environment. A central control can integrate
perception, action and reasoning in a consistent
way, since all those processes are subordinated to
the same goals. This integration may also provide
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