1. A method of tracking an object in an input image stream, said method comprising iteratively applying the steps of: (a) rendering a three-dimensional object model according to a previously predicted state vector from a previous tracking loop or a state vector from an initialisation step; (b) extracting a series of point features from said rendered object; (c) localising corresponding point features in said input image stream; (d) deriving a new state vector from said localised point feature in the input image stream.