An Affordance Based Model for Gameplay Dan Pinchbeck University of Portsmouth Eldon Building, Portsmouth PO1 2DJ [email protected]
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An affordance based model for gameplay Dan Pinchbeck University of Portsmouth Eldon Building, Portsmouth PO1 2DJ [email protected] ABSTRACT of these cases, the affordance is a quality designed and This paper presents a formal model for gameplay based embedded into a system. What is possible within a game is upon the affordances available to the player that are linked hardwired into the system as a network of affordances. A to game objects. It has been constructed via an extensive similar assertion is made by Calleja [4], Klevjer [14], analysis of major first-person games 1998-2008, although it Pinchbeck [17] and Wilhelmsson [22]. In other words, is argued it may extend to all diegetic games. Gameplay can within a ludic context, an affordance can be described as the be understood as a network of allowed actions, that can be functional input/output relationships of an object in the summarised as a small number of archetypal affordances context of the game environment. mediated by a set of parameters that define their functional relationships. As well as the capacity for the model to elucidate the ludic structures of games, it is argued that an However, whilst affordances have been used in games affordance based model also provides a means to research, what is missing is a formal model taxonimising understand the relationship and role of story and content the types of affordances normally embedded within a within a ludological context. system and how these relate to its objects. It is such a model that is proposed here. In order to do so, ludic objects are Author Keywords first categorised according to the states and parameters Affordances, gameplay models, content, ludology, theory. which define them. This taxonomy has been constructed through an analysis of 35 first person perspective titles AFFORDANCES AND GAMEPLAY released between 1998-2008. In what follows, the acronym Gibson's concept of affordances has been sporadically FPS is used for brevity, although it should be noted that applied to games for several years now, as a powerful tool neither the analysis nor the model is reduced to simply for understanding the relationship between player and shooters, and includes those games which blur the genre system. In particular, affordances offer a structured boundaries like Portal [21] Fallout 3 [2] and Pathologic framework for the interplay of interpretation, action and [12]. presentation that forms the basis of what Perron has called 'the heuristic cycle of gameplay'. [16] DEFINING OBJECTS: STATES AND PARAMETERS To begin with, all ludic objects can be divided into those with one state and those with at least two states. A state is Put simply, an affordance is an allowed action which can be defined as a set of properties that defines the object and its extracted by a user. Klevjer asserts that an affordance “does relationship to its context. Objects with only one internal not merely describe the conscious act of recognising state are those whose affordances only take one form and possibilities of successful interaction... but describes a cannot be altered by gameplay. Multiple state objects, in basic condition for there to be any meaningful visual contrast, are those in which the affordances can be altered, perceptions at all” [14]. Affordances thus rest upon a the simplest form of which is being removed from the fundamental extraction of the functions of the object or world. Affordances may change as play occurs; they are environment in question, rather than simply its properties. It defined by a series of parameters (normally integers) which is this extraction of available or supported actions that determine how they are enacted. A crate that can be broken, makes affordances such an appealing construct for game for example, has a parameter that defines the total damage it researchers. Linderoth & Bennerstedt, for example, argue can take before changing state (whole to broken). In this that “The basic perceptual act for a computer gamer is to case, the crate has two states; its affordances are determined pick up affordances in the game environment. She or he by which state it is in, and the state itself is a description of sees possibilities for how to interact with the game” [15]. the object's parameters. These states are fixed: so either the Gee extends this beyond perception, suggesting that state is triggered when the parameters are aligned with this affordances link to the epistemological act of play [7]. In all template (such as the depreciating damage counter of the Breaking New Ground: Innovation in Games, Play, Practice and Theory. Proceedings of DiGRA 2009 © 2009Authors & Digital Games Research Association (DiGRA). Personal and educational classroom use of this paper is allowed, commercial use requires specific permission from the author. crate reaching zero) or by an instantaneous shift in kit, on the other hand, can only be used in one way, whether parameters to a predetermined set (a door's parameters, it is activated by co-location or added to an inventory. defining affordances like whether one can move through it, see through it, etc, may be fixed to two states – open and closed). As a metaphor, the relationship between Another basic division can be made between affordances affordances, parameters and states can be seen as being like related to gameplay, and those related to diegesis. This a graphic equalizer. Bass, middle, treble, and so on, may all divides those affordances that have the capacity to affect be independently adjusted on their scale, yielding a other objects and those that do not, but may still exert different sound. However, the system may also include a influence upon the player's experience. In the former number of presets which instantaneously shift all category are objects such as Ladders, Flame Jets, Health parameters to predefined points on the scale. Thus, if an Kits, Buttons and Levers, Keycards, Agents and Spawn object is said to have more than one state, it means that the Points; in the latter Weather, Graffiti, small items such as object has at least two predetermined and fixed sets of cups or glasses, PDAs and Journals and Cutscene Triggers. affordance relationships, whether the parameters defining these may then be also individually manipulated or not. Finally, in each of these categories there is a scale of significance. For example, barrels may be used as cover in Thus, a static, unbreakable crate is defined by a number of many games, but Half Life 2 [18] greatly increases their parameters: its x, y and z co-ordinates. It may afford cover, significance with its use of the Gravity Gun, turning them or reduction in sightlines, or the ability to adjust the z co- into objects to be manipulated extensively in play. Beyond ordinates of an avatar if it can be stood upon. It is a single a level of significance, objects become critical, as their state object. If the crate in question is breakable, it has two affordances will or must always be triggered for play to states, controlled by a single parameter: the damage it can progress. Keycards that unlock previously inaccessible take. On taking damage, the integer defining this parameter areas are a generic device of this type, as are the Gravity reduces. When it reaches a certain value (normally zero), a Pathways and Spirit Walk sections of Prey [11]. By state change is effected. The other parameters defining the definition, a critically significant diegetic affordance must object are instantly changed: the corresponding visual also be a gameplay object: a code in a journal is not simply representation of the object is replaced with a pile of debris, a story affordance but renders the journal itself a critical which no longer affords the ability to adjust the z co- gameplay object. However, we can track a scale of ordinate of the avatar, or the ability to take cover and so on. significance in diegetic objects too; textures and posters If the crate can be pushed around by the avatar a new may not contribute directly to stories or story progression, affordance is added. Its other affordances remain constant, but act as corroborative detail, supporting the general although its significance for gameplay may be adjusted by diegesis. This is in contrast to those objects that explicitly the player taking advantage of these affordances (such as contribute to the story: diaries, journals, audio logs, and so reaching a new area). By moving the crate, the x and y co- on. ordinates are altered, but the state remains constant; there are no immediate shifts to the defining parameters across OBJECTS AND AFFORDANCES the board. This is an entirely distinct process to the state Fig 1 demonstrates that the range of objects found in FPS change that happens as a result of reducing the damage- games reduces to a small number of types. This should thus taking parameter to a pre-determined value (zero). In the be applied to how the state and parameter make-up of same way, a light switch has two states: on or off: a single objects mediate the affordances of a game system. binary parameter determining whether the surrounding area is illuminated or not. In this case, the only parameter shift that can be enacted is linked absolutely to a state change. In the 1STATE category, there are two classes of object: static and moving/movable. These objects cannot be altered by the act of play; although in the second class their Multiple state objects can be divided into those whose use location can change. Their impact upon gameplay and the is specifically defined and those that can be manipulated avatar is limited to response only.