1. A method of tracking an object of interest controlled by a user to interface with a computer, the method comprising: acquiring images from at least two viewpoints; processing the acquired images to produce an image data set for each acquired image; comparing each image data set to one or more background data sets to produce a difference map for each acquired image; detecting a relative position of an object of interest within each difference map; producing an absolute position of the object of interest from the relative positions of the object of interest; and using the absolute position to allow the user to interact with a computer application.