Sensing Ability of Wii Remote
The Wii Remote has the ability to sense acceleration along three axes through the use of an ADXL330 accelerometer. The Wii Remote also features a PixArt optical sensor, allowing it to determine where the Wii Remote is pointing.Unlike a light gun that senses light from a television screen, the Wii Remote senses light from the console’s Sensor Bar (model number RVL-014), which allows consistent usage regardless of a television’s type or size. The Sensor Bar is about 20 cm (8 in) in length and features ten infrared LEDs, with five LEDs being arranged at each end of the bar In each group of five LEDs, the LED farthest away from the center is pointed slightly away from the center, the LED closest to the center is pointed slightly toward the center, while the three LEDs between them are pointed straight forward and grouped together. The Sensor Bar’s cable is 353 cm (11 ft 7 in) in length. The bar may be placed above or below the television, and should be centered. If placed above, the sensor should be in line with the front of the television, and if placed below, should be in line with the front of the surface the television is placed on. It is not necessary to point directly at the Sensor Bar, but pointing significantly away from the bar will disrupt position-sensing ability due to the limited viewing angle of the Wii Remote.Use of the Sensor Bar allows the Wii Remote to be used as an accurate pointing device up to 5 meters (approx. 16 ft) away from the bar.The Wii Remote’s image sensor is used to locate the Sensor Bar’s points of light in the Wii Remote’s field of view. The light emitted from each end of the Sensor Bar is focused onto the image sensor which sees the light as two bright dots separated by a distance “mi” on the image sensor. The second distance “m” between the two clusters of light emitters in the Sensor Bar is a fixed distance. From these two distances m and mi, the Wii CPU calculates the distance between the Wii Remote and the Sensor Bar using triangulation.In addition, rotation of the Wii Remote with respect to the ground can also be calculated from the relative angle of the two dots of light on the image sensor.Games can be programmed to sense whether the image sensor is covered, which is demonstrated in a Microgame of Smooth Moves, where if the player does not uncover the sensor, the champagne bottle that the remote represents will not open.The Sensor Bar is required when the Wii Remote is controlling up-down, left-right motion of a cursor or reticle on the TV screen to point to menu options or objects such as enemies in first person shooters. Because the Sensor Bar also allows the Wii Remote to calculate the distance between the Wii Remote and the Sensor Bar, the Wii Remote can also control slow forward-backward motion of an object in a 3-dimensional game.Rapid forward-backward motion, such as punching in a boxing game, is controlled by the acceleration sensors. Using these acceleration sensors (acting as tilt sensors), the Wii Remote can also control rotation of a cursor or other objects.The use of an infrared sensor to detect position can cause some detection problems when other infrared sources are around, such as incandescent light bulbs or candles. This can be easily alleviated by using fluorescent lights around the Wii, which emit little to no infrared light.Innovative users have used other sources of IR light as Sensor Bar substitutes such as a pair of flashlights and a pair of candles.Such substitutes for the Sensor Bar illustrate the fact that a pair of non-moving lights provide continuous calibration of the direction that the Wii Remote is pointing and its physical location relative to the light sources. There is no way to calibrate the position of the cursor relative to where the user is pointing the controller without the two stable reference sources of light provided by the Sensor Bar or substitutes.The position and motion tracking of the Wii Remote allows the player to mimic actual game actions, such as swinging a sword or aiming a gun, instead of simply pressing buttons. An early marketing video showed actors miming actions such as fishing, cooking, drumming, conducting a string quartet, shooting a gun, sword fighting, and performing dental surgery.