Hardware Reference
In-Depth Information
Sensor Bar
Camera
3-Axis Accelerometer
z
y
x
Figure 2-35.
The Wiimote video game controller motion sensors.
swing the Wiimote to hit a virtual tennis ball, the motion of the Wiimote is tracked
as you swing toward the ball, and if you twist your wrist at the last moment to put
topspin on the ball, the Wiimote accelerometers will sense that motion as well.
While the accelerometers perform well at tracking the motion of the Wiimote
as it moves in three dimensions, they cannot provide the fine-grained motion sens-
ing necessary to control a pointer on the television screen. The accelerometers suf-
fer from unavoidable tiny errors in their acceleration measurements, thus over time
the exact location of the Wiimote (based on integration of its accelerations) will
become increasingly inaccurate.
To provide fine-grained motion sensing, the Wiimote utilizes a clever computer
vision technology. Sitting atop the television is a ''sensor bar'' which contains
LEDs a fixed width apart. Contained in the Wiimote is a camera that when pointed
