Recent Online and Multiplayer Games 33
Telepresence uses computers and networks to provide a feeling of immersiveness for a user that is physically separated from the environment. Sensors gathering information on the local environment transmit information to a physically separated user, providing feedback that allows some recreation of the local world from the remote location.
With telepresence, managing latency is critical for providing a feeling of immersiveness. In the local world, an action has an immediate consequence, whereas in telepresence, an action done remotely is delayed by the time it takes to travel from the remote user to the local environment, plus any additional processing time. Force feedback, where tension or pressure occurs from physically manipulating the local environment, is also often necessary to make the remote user immersed in the local world and can often help overcome deficiencies in the display from a low resolution or frame rate [MS94].
Another example of telepresence is computer-assisted surgery, which is gaining in popularity because it allows specialists to provide medical care to a geographically broader audience, as well as providing opportunities for computers to make surgeons more precise. When there are concerns about hazardous environments, this brings telepresence to the front line of battlefields, allowing surgeons to aid soldiers during combat.
Telepresence in education can allow people to experience environmentally fragile loca-tions, such as the coral reefs or Egyptian tombs. Space exploration can also benefit from telepresence, as in operating a rover on Mars from Earth [http://marsrovers.jpl.nasa.gov/ home/]. Telepresence systems could even be incorporated in entertainment systems beyond games, by allowing the experience of a roller coaster or sky-dive without the associ-ated risks.
As an example that augments reality even more, consider the original Pacman game that featured the well-known, cookie-shaped disk that game players manoeuvred through maze munching dots. An AR version of the game called Human Pacman depicted in Figure 3.22 [CFG+03] has game players assume the role of the gobbling disk where the physical world is augmented with virtual dots the players see by means of a wearable computer with a head-mounted display. Sensors on the display indicate the direction the player is looking and the GPS provides positional information to generate virtual dots at the appropriate physical locations. Multiplayer aspects are incorporated by having some players assume the role of the ghosts that chase Pacman. Bluetooth technology provides networking to enable the Pacman player to ‘pickup’ power pills to then chase the ghosts. Human Pacman goes beyond basic Pacman gameplay of one yellow disc against all the ghosts by enabling an additional player to see an overview of the game field on a networked computer, then relaying information about the location of ghosts and power pills to the human Pacman (Figure 3.23).
FPSs have also entered the AR game space, notably with ARQuake an AR version of the popular Quake game [PT02]. ARQuake players as in Figure 3.24 use a head-mounted