1. A computing device in a system for motion detection, the computing device comprising: an image processing device to determine a motion of an object of interest; and a graphical user interface (GUI) module to drive a virtual role based on the motion determined by the image processing device, the image processing device comprising: a foreground extracting module to extract a foreground image from each of a first image of the object of interest taken by a first camera and a second image of the object of interest taken by a second camera; a feature point detecting module to detect feature points in the foreground image; a depth calculating module to calculate the depth of each of the feature points based on disparity images associated with the each feature point, the depth calculating module and the feature point detecting module identifying a three-dimensional (3D) position of each of the feature points, wherein the depth calculating module includes: a disparity image searching unit to search for disparity images associated with a feature point based on the foreground image each of the first and second images, and a search unit to search for the feature point based on the disparity images; and a motion matching module to identify vectors associated with the 3D positions of the feature points and determine a motion of the object of interest based on the vectors.