Periodicity
In any one figure, the frequencies of sine functions controlling angles in the joints are set to be either equal or having ratios of 2.0 or 0.5. For instance, one joint angle sine function may have a frequency of F, and another might have a frequency of F/2 or F*2. Having whole-number frequency ratios encourages periodic motions in the figures - every gesture the figure makes is certain to be repeated over and over again as the animation runs. This is helpful for the acquisition of locomotion skills, in which periodicity can help (and it makes them potentially good dancers as well). But, as we shall see in the discussion on the gesture tool below, this can impose constraints on the matching of figure motions with the user's gesture.
PHYSICS
