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< Contents ERCIM News No. 57, April 2004

NetAttack - First Steps towards Pervasive Gaming

by Irma Lindt and Wolfgang Broll

While console and desktop-based computer games are becoming ubiquitous in our everyday lives, computer games that sense their physical environment are still quite rare. Most current computer games tie their players to a single room, preventing them from the outdoor experience offered, for example, by many children's games. A sensible way of integrating computer games into our physical environment is to use Augmented Reality (AR) technology. Augmented Reality enhances our physical world with synthetic objects, transforming our physical world into a pervasive game experience.

The first graphical computer game - a simulation of noughts and crosses called Tic-Tac-Toe - was written by A.S. Douglas in 1952. Based on the limited capabilities of early computers, the user interface of Tic-Tac-Toe was quite simple: the CRT display had a resolution of 35x16 pixels and the player placed his nought or cross using a mechanical telephone dialer.

Since then, desktop- and console-based games have developed into sophisticated 3D environments, and can respond to user input in real time. The have become a huge market and a driving force of the computer industry, and the development of new computer games often goes hand in hand with the development of computer technology. As a logical consequence, computer games will also follow the latest trend of pervasive computing.

There are already numerous games that run on mobile devices such as cellular phones or handhelds, but only a few of these can sense their physical environment. NetAttack is a new type of indoor/outdoor Augmented Reality game that makes the actual physical environment an inherent part of the game itself.

The game experience depends on whether you choose to be an indoor or an outdoor player. The indoor player sits in front of a desktop computer and supports the outdoor player with valuable information, such as where to find hidden items, how to delay or disadvantage competing teams and what to do next to win the game (Figure 2). The outdoor player, equipped with a backpack full of technology, rushes around a predefined game field trying to collect items. The game time is limited and ensures the game is fast-paced.

The goal of the game is to destroy the central database of a big (virtual) corporation. In order to achieve this goal, teams must compete for items that will finally allow them to compose a secret password, thereby enabling them to destroy the database. Actions and moves depend on individual position, the competing teams and communication within a team.

We have implemented NetAttack based on our AR framework using laptop computers and personal displays. Outdoor players are equipped with GPS receivers, inertial trackers and video cameras to determine their positions and orientations. Computer-vision tracking is used to refine the GPS-tracking data. Data from various sensors are merged using sensor fusion to obtain the necessary precision. Head-sets support communication between the players of each team.

NetAttack is implemented as a distributed application. The various components communicate via events and a TCP/IP-based high-level protocol. A central component guarantees consistency and allows the configuration of the game. Before starting to play the game, the outdoor game area must be modelled and the game levels configured. The configuration is done with XML. For each game level, variables such as the game area, number and position of the game items and the playing time may be defined.

Initial experiments with volunteers (students and researchers from our institute) have been conducted on our campus. In our current set-up, two teams compete, each consisting of one outdoor and one indoor player. The hidden 3D items are distributed over the campus (Figure 1). Currently the outdoor experience is limited to a designated area on the campus that provides sufficient wireless network coverage. On several occasions during the year, the game will also be made available to the public.

Figure 1: Outdoor player looking for a virtual game item.
Figure 1: Outdoor player looking for a virtual game item.
Figure 2: Indoor player with a map of the game area and an overview of the collected game items. A yellow dot within the map indicates the current position of the outdoor player.

Future Work
We plan to continue developing and improving the current version of the game, providing easier and more powerful configurations and authoring possibilities, and extending the actual playing area. In addition to wider WLAN coverage, a version based on mobile phones (GPRS or UMTS) is anticipated. Other extensions are the use of alternative input and display devices, including but not limited to PDAs.


Please contact:
Irma Lindt, Fraunhofer FIT
Tel: +49 2241 14 2206