FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Three-Dimensional Input Devices
A three-dimensional device delivers three data values simultaneously. Such devices are rare but are becoming more common as the game industry begins to adopt motion-sensing devices like the Wii Remote.
An accelerometer is not a switch or button that the player directly manipulates. It is an electronic device that measures the rate of acceleration it experiences. Game hardware manufacturers build accelerometers into controllers such as the Wii Remote so the player can wave the controller around rather than simply hold it and press buttons. With the data from multiple accelerometers, you can compute how far and how fast the player moves the remote, and in what direction. The Nintendo Wii Remote and Nunchuck, and the Apple iPhone, are the best-known devices that use accelerometers in gaming.
When an accelerometer is at rest with respect to the Earth (sitting still on a table, for example), it reports the force of gravity. This means that you can also use an accelerometer as a tilt sensor. If the acceleration of gravity appears to change direction, it means the device has been tilted with respect to the ground. You can also detect if the player has turned it upside down: The direction of the acceleration of gravity will be reversed.
An accelerometer returns absolute acceleration information. If it were in zero gravity and undergoing no acceleration, it would return zero in all three dimensions.
Global positioning systems have become commonplace in high-end mobile phones, and it won't be long before they are ubiquitous in phones, personal digital assistants (PDAs), and handheld gaming devices. A GPS returns the device's latitude and longitude on the surface of the Earth, as well as the altitude above sea level. The player uses a GPS as input to a game by moving the GPS around in the environment. The UK-based art collective Blast Theory has constructed several augmented reality games that use global positioning systems. Players travel around a cityscape on foot, carrying a GPS-enabled device that helps them play the game.
GPS devices return absolute positional information. By taking measurements over time, you can use this data to compute the player's speed and direction.
GPS devices have two significant drawbacks at the moment. First, because they need to receive data from satellites orbiting the Earth, they only work in areas where they can easily receive the satellites' transmissions—usually outdoors. Second, the current generation of GPS technology is only accurate to within several meters, so they're only useful on a large scale. The European Galileo satellite navigation system, which is due to come online in 2013, is designed to be accurate to the 1-meter range.
|
|