Algorithm 1
An overview of the proposed algorithm.
Step 1. Initialization (at time )  (i) : the number of tracked hands  (ii) : the displacement of one interesting point from time to  (iii) : minimum number of interesting points  (iv) Manually Initialize the sets , (such as at time in Figures 6–12)  , .  (v) Find interesting points in via goodfeaturetotrack [7, 21].  For at time  Step 2.  (i) Find interesting points using via optical flow [22].  (ii) If obtain the final interest points .  (iii) Compute the hands mean velocity , using via (11).  (iv) Predict the sets , using .  Step 3.  Build the graph and apply expansion via (19).  Step 4.  If < (the number of interest points below a given threshold )  Update interesting points in the region via goodfeaturetotrack [7, 21].  If <  Return to Step 2. 
