Computer games -- and their virtual 3D worlds in particular -- have been a main driver of very rapid technological development over the past few years, creating a significant segment of the international entertainment industry. Today, the PC games and console games that dominate the market tie the players to their monitors and controls. Games on mobile phones or PDAs may be played anywhere, but they also aim to focus the players' attention away from their real environments.
Just a few advanced games go beyond the virtual world- paradigm, attempt to integrate the gamers' real environment in the game and to let the players perceive -- and act in -- their actual physical environment. Augmented Reality technologies now let us do just that, allowing game designers to start from a real physical environment and enhance it with virtual objects to create novel exciting games in an augmented reality-setting.
NetAttack is one such novel indoor / outdoor mixed reality computer-based game whose playing field is a real physical setting where the players can move about freely.
A cracker team consists of an Agent and an Operator. The Agent does the outdoor field work, wearing a helmet that has the personal display and the tracking system attached. The Operator works from a stationary computer, using an audio link to communicate with the agent and help her navigate the game world. The operator's main tool is a map of the game world that shows the positions of various virtual objects and the current position of his agent. Agent and operator need to cooperate and share the information each has available.
To allow an unlimited number of cracker teams in the game simultaneously, NetAttack is a distributed system whose modules communicate via Wi-Fi network. A central server manages intra-team communication and the overall state of the game, consumption of resources, allocation of virtual objects etc. as well as communication of specific events among teams.
To make sure that virtual objects are always perceived in the correct spot in the real setting, the system needs to 'know' the agent's position in the real setting and where exactly she is looking. A combination of tracking technologies is used to provide that information in NetAttack: Broad positioning is taken from GPS. Precision is significantly enhanced based on computer vision. An orientation sensor on the agent's helmet determines with great precision where s/he looks.