1. A system comprising: at least one device processor; and a machine readable storage device storing executable instructions that, when executed, cause the at least one device processor to: receive, from one or more cameras, three-dimensional (3-D) spatial image data associated with at least one arm motion of an actor based on free-form movements of at least one hand of the actor, based on natural gesture motions of the at least one hand; determine a plurality of sequential 3-D spatial representations that each include 3-D spatial map data corresponding to a 3-D posture and position of the at least one hand at sequential instances of time during the free-form movements, based on the received 3-D spatial image data; and generate an integrated 3-D model based on incrementally aggregating the 3-D spatial map data included in the determined sequential 3-D spatial representations and comparing a threshold time value with model time values indicating numbers of instances of time spent by the at least one hand occupying a plurality of 3-D spatial regions during the free-form movements.