1. A computing device for motion detection in a system capable of detecting feature points of an object of interest, the computing device comprising: a vector forming unit to form a plurality of vectors associated with a set of the feature points and form a vector set represent a predetermined posture based on the vectors; a posture identifying unit to identify a match of a posture in a database based on the vector set; a motion similarity unit to identify a set of predetermined postures represent a predetermined motion in the database based on the matched posture and an immediately previous matched posture; and a motion identifying unit to identify the predetermined motion in the database based on the set of predetermined postures.