Artificial Game Presenter Avatars Anthony Savidis1,2, Effie Karouzaki1
1Institute of Computer Science, FORTH
2Department of Computer Science, University of Crete
{as,karuzaki}@ics.forth.gr
ABSTRACT
We propose artificial game presenter avatars embodying affective
behavior to draw player-adapted social feedback during gameplay
and introducing extra challenges to players called mini games,
such as hangman and random card selection. The avatar’s AI was
designed as an extension of the traditional sense-think-act loop of
game characters to address the need for emotional reflection and
adaptive reaction. We provide a cartoon-like 2d delivery for our
avatar, however, one could support alternative approaches for
rendering and animation.
1. INTRODUCTION Our work is motivated by the popularity of television game shows
and the lack of an analogy in the domain of computer-based
entertainment. Technically, all games played in such shows are
multiplayer computer games with a technological setup
amplifying social interaction. Essentially, the game presenter
provokes social interaction to keep the players and the audience
constantly motivated and alerted about the game progress. For this
purpose, a show presenter relies on player profiles, current
challenge and previous performance to provide feedback
commonly involving humor, reward, sympathy, surprise,
disappointment, enthusiasm, agony and anticipation. Clearly,
presenters display an affective behavior. In this context, we have
developed an artificial game-presenter avatar, named Amby, as a
software system that can be incorporated in turn-taking
multiplayer games. Amby was created to support the concept of
multiplayer computer games hosted by artificial avatars as
illustrated within Figure 1, top left. The top right part of Figure 1
shows how Amby has been incorporated within a pervasive
board-game named Four Elements1 [2] with an overall physical
setup inspired from game shows. To our knowledge there is no
similar work proposing or implementing the idea of an artificial
1 A video of the Four Elements game is available from:
http://www.ics.forth.gr/hci/files/plang/BoardGameVide(High%2
0res).wmv and a video of Amby in a play session is available
from: http://www.ics.forth.gr/hci/files/plang/AmbyVideo.avi
Permission to make digital or hard copies of all or part of this work for
personal or classroom use is granted without fee provided that copies
are not made or distributed for profit or commercial advantage and that
copies bear this notice and the full citation on the first page. To copy
otherwise, or republish, to post on servers or to redistribute to lists,
requires prior specific permission and/or a fee.
Artificial
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Figure 1. The concept of computer games with artificial presenter avatars and its instantiation with our avatar.
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Figure 2: The domain of our work (left), the enhanced behavior loop (middle) and the affective state space of our avatar (right).
Permission to make digital or hard copies of part or all of this work or personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee.Ace 2009, Oct 29-Oct 31, 2009, Athens, Greece© ACM 2009 ISBN: 978-1-60558-864-3/09/10...$10.00
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presenter avatar for computer-games supporting affective behavior
and player-adapted social reactions. Technically our work falls in
the intersection of the four domains depicted under Figure 2, left.
2. BEHAVIOR The behavior loop of our avatar is an improvement of the
traditional sense-think-act loop (see Figure 2, middle) for game
characters introducing reflect and adapt as two extra processing
stages. We logically split avatar reactions in two levels: (a)
abstract reactions, denoting the general reaction category; and (b)
concrete reactions, being alternative ways of specializing abstract
reactions. Comparing to the Circumplex model [1] we dropped a
few aspects (see being meaningless in a game context: (i) ‘fear’
and ‘disgust’ emotions; (ii) distinction among ‘activation’ and
‘deactivation’ (i.e. no tangible trophy); and (iii) intermediate
states for sadness like ‘guilt’ or ‘depression’ (see Figure 2, right).
The reflect process is implemented as a hybrid state transition
network with transitions involving condition expressions
(predicates). Player emotions relate to distinct affective states thus
the transition logic is affect computation. In practice, emotional
changes heavily depend on the summative effect of other game
incidents (events). For this purpose we introduced summative
variables that can be involved in transition predicates, together
with memory variables, normally recording game events.
3. ARCHITECTURE The overall architecture is illustrated under Figure 3, left part,
showing the split amongst the decision rules categories (such as
think and reflect), as well as the various external libraries
deployed encompassing data required for the implementation of
the avatar physical reactions (such as images, audio files and
expression animations). Also, the dual role of the avatar User
Interface is outlined: (a) as a server of “reaction” requests coming
from the avatar AI component; and (b) as a server of game hosting
requests coming directly from the game to support inventory,
player display, turn taking functionality, and mini games. All
communication between the avatar and the AI module or the game
core takes places over the network custom protocols. A couple of
scenes from hangman game sessions are shown under Figure 3,
right part, illustrating the respective emotion states.
4. SUMMARY Our work is motivated by the huge popularity of television game
shows and the key role of the presenter towards their success. For
this purpose we introduced the notion of an artificial game-
presenter avatar and we identified affective adaptive behavior to
be the most important feature towards this direction. Clearly,
anthropomorphism and quality of representation are other highly-
critical dimensions that we do not address in the context of our
work. To accomplish affective behavior we have implemented a
scalable architecture relying on adaptation-processing loops. To
our knowledge no earlier work proposed computer-games as
socially-stimulating experiences motivating social peers to watch
play sessions as in typical television game shows. In making the
artificial intelligence core of our avatar we adopted a decision
specification language we developed earlier named DMSL [3],
while we have embedded its interpreter as part of the avatar
implementation system.
The primary extensions we introduced to the basic sense-think-act
behavior processing concerned: (a) a reflect stage to derive
players emotions (affective processing); and (b) an adapt stage to
specialize avatar reactions in ways bets-fitting individual player
profiles. An extra feature we included is the on-the-fly generation
of a textual script in the form of dialogues amongst players and
the avatar. As part of our future extensions we work on the
structuring of rule libraries in ways enabling meta-rules choose
alternative avatar behavior styles such as humorous, ironic,
teasing or compassionate.
5. REFERENCES [1] J. Russell, G. Lemay (2000). Emotion Concepts. In
Handbook of Emotion, M. Lewis, M. Haviland-Jones (Eds.),
New York: Guilford Press.
[2] A. Savidis, Y. Lilis (2008). Adaptable pluggable multimodal
input with extensible accessible soft dialogues for games. In
ACM ACE 2008 Int. Conf. on Advances in Computer
Entertainment, pp. 155-158.
[3] A. Savidis, M. Antona, C. Stephanidis (2005). A Decision-
making Specification Language for Verifiable User-interface
Adaptation Logic. Journal of Software Engineering and
Knowledge Engineering, Volume 15, Issue 6 (December
2005), pp. 1063-1094.
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Figure 3. Software architecture of our avatar (left), and details of the User Interface component architecture (right).
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