Narrative in Virtual Environments - Towards Emergent Narrative Ruth Aylett Centre for Virtual Environments Business House, Universityof Salford Salford M5 4WT, UK r.s,aylett @salford.ac.uk Abstract In this paperweconsiderthe clash between the pre-scripted character of much narrative and the freedom afforded by a Virtual Environment. We discuss the concept of emergent narrative as a possible wayof avoiding this clash. We examine the role of a VE user in a narrative and considerthe concept of social presence as a means of reconciling the freedom of the user with the constraints of an emergent narrative. Introduction This short paper describes preliminary thoughts - rather than completedwork - on narrative issues arising from a recent project ’Virtual Teletubbies’ [Aylett et al 99]. In this project, children’s TV characters - Teletubbies - were incorporated into a virtual environment (VE), by which we mean a graphically rendered world in which both they and the user have a joint spatial existence. In this case, the user was not required to use special immersivehardware, such as a head- mounted display, but was represented by an invisible camera position attached to spatial controls which allowed him or her to ’move’within the VE. The Teletubbies were implemented using a behavioural robot architecture, in which emergent behaviour at a given moment is determined by the synthesis of responses from currently active behaviour patterns [Barnes 96]. These behaviour patterns are in turn driven by simple virtual sensors while groups of behaviour patterns (packets) are activated or deactivated according to the level of the Teletubbies’ internal drives, such as hunger, fatigue and curiosity. As with robots, the initial behaviours implemented were those allowing physical movement in the environment, in this case taking into account the sloping nature of the outdoor terrain being modelled. A simple form of gravity was also modelledso that neither Teletubbies nor user were able to ’fly’ within the VE. Virtual sensors were implemented as bounding boxes and as a forward sweeping sensor for obstacle avoidance; information about objects in a Teletubby line-of- sight was transferred directly as symbolicinformation rather than through a virtual retina. While this project was successful in examiningsome basic architectural issues, a number of issues of narrative arose, manyof which are common to virtual environments of other types. We consider the problem of narrative as it arose in this particular project, examine alternative ways of dealing with the issues, and sketch out a wayforward which involves an approach to narrative webelieve has not yet been very widely investigated. A Narrative Problem In moving characters from television to VE, the difficulty in retaining the original narrative approach was immediately evident. Ontelevision, the narrative is normallywhollypre- scripted and is viewedpassively by the audience from camera positions determined by the creators of the narrative. However, translating this directly into a VE removes all the characteristics that differentiate a VE from television. The ability of the user to interact individually with the VE and eventheir ability to select their spatial viewpoint is deniedin this approach. While the narrative experience fails to exploit the characteristics of a VE,there can of course be a change in the process of narrative production. Through the provision of an appropriate toolkit, characters in a VEcan be treated as virtual actors and the user can construct narratives in which they appear. This approach has been investigated by a number of groups, in 2D multi-media environments as well as in VEs, as for examplethe ’Virtual Theater’ project of Barbara Hayes-Roth [Hayes-Roth & Brownston 95] and the IMPROV virtual actors system [Goldberg 97]. As welt as empowering users whowould normally be excluded from the creation of 3Dspatially located narrative, this approachis also of interest to the film industry. Directors are beginning to exploit the power of 3D graphic environments explicitly in films such as ’Toy Story’ and ’Antz’ and implicitly via special effects in films such as ’Titanic’. Nevertheless, the extension of freedom in the process of narrative construction does not in our view remove the need to examine how the narrative experience might be extended to take advantage of the specific characteristics of a VE. Two issues are of interest here. The first is howfar the pre-determined nature of much narrative can be relaxed. The secondis how far the user of a VE can freely participate in a narrative rather than acting as a spectator. Clearly these issues are related - a wholly pre-determined narrative also pre- determines the role, if any, of the user within it. Thus relaxing this constraint allows more freedom for user 83 From: AAAI Technical Report FS-99-01. Compilation copyright © 1999, AAAI (www.aaai.org). All rights reserved.