Fig. 1. General outline of the system.

Fig. 2. Feature extraction mechanism (shown for the gesture “point to the left” for θ=45, l=20, K=2, X=2; see text for details). All possible binary transition patterns [p₁(t), p₂(l,nθ,t), p₁(t+1), p₂(l,nθ,t+1)] for different values of nθ and l are extracted and integrated, as the circular areas are shifted across the sequential images B(t) and B(t+1).

Fig. 3. Gesture trajectories in discriminant feature space for four classes of gestures. Class averages for each class are displayed by solid lines, while trajectories of the corresponding test samples (which have not been used during the training process) are shown in dashed lines.

Fig. 4. Information processing flow performed by the dynamic buffer structures (DBS). Details are given in the text.

Fig. 5. Snapshots of some of the gestures used in Experiment 3.1 (MMDB database). The following gestures are shown: “me” (top), “left circle” (middle) and “expand” (bottom).

Fig. 6. Snapshots of some of the gestures used in Experiment 3.2(b) (different subjects). The following gestures are shown: “clap hands” (top), “cross” (middle) and “banzai” (bottom).

Fig. 7. Snapshots of some of the gestures used in Experiment 3.2(c). The gesture “right hand up” is shown in three different background and illumination conditions.