Mobile experiences that take place in public settings such as on city streets create new opportunities for interweaving the fictional world of a performance or game with the everyday physical world. A study of a touring performance reveals how designers generated excitement and dramatic tension by implicating bystanders and encouraging the (apparent) crossing of normal boundaries of behaviour. The study also shows how designers dealt with associated risks through a process of careful orchestration. Consequently, we extend an existing framework for designing spectator interfaces with the concept of performance frames, enabling us to distinguish audience from bystanders. We conclude that using ambiguity to blur the frame can be a powerful design tactic, empowering players to willingly suspend disbelief, so long as a safety-net of orchestration ensures that they do not stray into genuine difficulty.

We present a study of a mobile mixed reality game calledCan You See Me Now?in which online players are chased through a virtual model of a city by ‘runners’ (professional performers equipped with GPS and WiFi technologies) who have to run through the actual city streets in order to catch the players. We present an ethnographic study of the game as it toured through two different cities and draws upon video recordings of online players, runners, technical support crew, and also on system logs of text communication. Our study reveals the diverse ways in which online players experienced the uncertainties inherent in GPS and WiFi, including being mostly unaware of them, but sometimes seeing them as problems, or treating the as a designed feature of the game, and even occasionally exploiting them within gameplay. In contrast, the runners and technical crew were fully aware of these uncertainties and continually battled against them through an ongoing and distributed process of orchestration. As a result, we encourage designers to deal with such uncertainties as a fundamental characteristic of location-based experiences rather than treating them as exceptions or bugs that might be ironed out in the future. We argue that designers should explicitly consider four potential states of being of a mobile participant: connected and tracked, connected but not tracked, tracked but not connected, and neither connected nor tracked. We then introduce five strategies that might be used to deal with uncertainty in these different states for different kinds of participant: remove it, hide it, manage it, reveal it, and exploit it. Finally, we present proposals for new orchestration interfaces that reveal the ‘seams’ in the underlying technical infrastructure by visualizing the recent performance of GPS and WiFi and predicting the likely future performance of GPS.

We study a collaborative location-based game in which groups of 'lions' hunt together on a virtual savannah that is overlaid on an open playing field. The game implements a straight-forward approach to location-based triggering in which players must be in the same spatial locale in order to share information and act together. Comparison of video recordings of physical play with system recordings of game events reveals subtle and complex interactions between highly dynamic player behavior and the underlying technology. While players exhibit a fluid approach to group formation, the system embodies a more rigid view, leading to difficulties with sharing context and coordinating actions, most notably when groups of players span virtual locale boundaries or initiate actions while on the move. We propose techniques for extending locales to support more flexible grouping and also discuss the broader implications of our findings for location-based applications in general.

Pervasive gaming is a new form of multimedia entertainment that extends the traditional computer gaming experience out into the real world. Through a combination of personal devices, positioning systems and other multimedia sensors, combined with wireless networking, a pervasive game can respond to a player's movements and context and enable them to communicate with a game server and other players. We review recent examples of pervasive games in order to explain their distinctive characteristics as multimedia applications. We then consider the challenge of scaling pervasive games to include potentially very large numbers of players. We propose a new approach based upon a campaign model in which individuals, local groups and experts draw on a combination of pervasive games, online services and broadcasting to take part in national or even global events. We discuss the challenges that this raises for further research.

Successfully staging a mixed reality game in which online players are chased through a virtual city by runners located in the real world requires extensive orchestration work. An ethnographic study shows how this concerted achievement extends beyond the control room to the runners on the street. This, in turn, suggests the need to 'decentralize' orchestration and develop support for collaboration 'on the ground'. The study leads to design proposals for orchestration interfaces for mobile experiences that augment situational awareness and surreptitious monitoring among mobile participants and support troubleshooting in situations where participants are disconnected or are unable to access positioning systems such as GPS.

We present four contrasting interfaces to allow multiple viewers to explore 3D recordings of dramas in on-line virtual worlds. The first is an on-line promenade performance to an audience of avatars. The second is a form of immersive cinema, with multiple simultaneous viewpoints. The third is a tabletop projection surface that allows viewers to select detailed views from a bird's-eye overview. The fourth is a linear television broadcast created by a director or editor. A comparison of these examples shows how a viewing audience can exploit four general resources - interactivity, influence, space, and time - to make sense of complex, non-linear virtual drama. These resources provide interaction designers with a general framework for defining the relationship between the audience and the 3D content.

Virtual reality (VR) currently lacks the kinds of sophisticated production technologies that are commonly available for established media such as video and audio. This paper introduces the idea of temporal links, which provide a flexible mechanism for replaying past or recent recordings of virtual environments within other real-time virtual environments. Their flexibility arises from a combination of temporal, spatial and presentational properties. Temporal properties determine the relationship between time in a live environment and time in a recording, including the apparent speed and direction of replay. Spatial properties determine the spatial relationship between the environment and the recording. Presentational properties determine the appearance of the recording within the environment. These properties may be fixed, dynamically varied by an application, or directly controlled in real-time by users. Consequently, temporal links have a wide variety of potential uses, including supporting post-production tools for virtual environments, post-exercise debriefing in training simulators, and asynchranous communication such as VR email, as well as providing new forms of content for virtual worlds that refer to past activity. We define temporal links and their properties and describe their implementation in the MASSIVE-3 Collaborative Virtual Environment (CVE) system, focusing on the underlying record and replay mechanisms. We also demonstrate applications for adding new content to an existing virtual world, and a VR post-production editor.