Figure 4: Tracking on the grey scale sequence Walk. Top two rows: method in [13]: the active curve encroaches on the object region though the blur between the walker feet and the grassy ground and continues drifting in due to the smoothness term and the uncertain outcome of intensity matching within the object uniform area. Third row: tracking with the method in [10]: the region intensity histogram representation allowed only a gross outline of the object. Bottom two rows: proposed method: by constraining the curve to retain a similar shape between consecutive frames, encroachment on the object and subsequent movement inward are averted.