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  • Artificial Game Presenter Avatars Anthony Savidis1,2, Effie Karouzaki1

    1 Institute of Computer Science, FORTH

    2 Department 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

    Game

    Presenter

    Primary Game

    Terrain

    Roundtable Player Positions

    Enthusiasm,

    Positive surprise Artificial

    Game

    Presenter

    Primary Game

    Terrain

    Roundtable Player Positions

    Artificial

    Game

    Presenter

    Primary Game

    Terrain

    Roundtable Player Positions

    Enthusiasm,

    Positive surprise

    Figure 1. The concept of computer games with artificial presenter avatars and its instantiation with our avatar.

    Artificial

    Avatars

    Affective

    Computing Game

    Characters

    Adaptive

    Interaction

    Focus

    Area

    Artificial

    Avatars

    Affective

    Computing Game

    Characters

    Adaptive

    Interaction

    Artificial

    Avatars

    Affective

    Computing Game

    Characters

    Adaptive

    Interaction

    Focus

    Area

    1.Sense

    2.Reflect 3.Think

    4.Adapt

    5.React

    E xte rn a l S tim u li

    Af fe cti ve S ta tes

    Abstract Reactions

    C o n c re te R e a c ti o n s

    Performing Actions

    1.Sense

    2.Reflect 3.Think

    4.Adapt

    5.React

    E xte rn a l S tim u li

    Af fe cti ve S ta tes

    Abstract Reactions

    C o n c re te R e a c ti o n s

    Performing Actions

    Happiness

    Enthusiasm

    Disappointment

    Sadness

    Positive / Negative

    Anticipation

    Negative / Positive

    Anticipation

    Encouragement /

    Discouragement

    Calm

    Anger

    AnxietyReassurance

    Encouragement /

    Discouragement

    Discouragement /

    Encouragement

    Discouragement /

    Encouragement

    Happiness

    Enthusiasm

    Disappointment

    Sadness

    Positive / Negative

    Anticipation

    Negative / Positive

    Anticipation

    Encouragement /

    Discouragement

    Calm

    Anger

    AnxietyReassurance

    Encouragement /

    Discouragement

    Discouragement /

    Encouragement

    Discouragement /

    Encouragement

    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.

    2009, -Oct , 2009, © ACM 2009 ISBN: 978-1-60558- - /09/ 0...$10.00

    415

  • 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-th