1. A real-time gesture based interactive system, comprising: a processor; a reference camera configured to capture sequences of frames of video data, where each frame of video data comprises intensity information for a plurality of pixels; memory containing: a hand tracking application; and a set of edge feature templates comprising a plurality of edge feature templates that are rotated and scaled versions of a base template; and wherein the hand tracking application configures the processor to: obtain a sequence of frames of video data from the reference camera; compare successive frames of video data from the sequence of frames of video data for pixels that change from one frame to the next; determine whether any of the pixels that changed are part of a human hand visible in the sequence of frames of video data by searching the frame of video data for a grouping of pixels that have image gradient orientations that match the edge features of one of the plurality of edge feature templates; and track a motion of the part of the human hand visible in the sequence of frames of video data; confirm that the tracked motion of the part of the human hand visible in the sequence of frames of video data corresponds to a predetermined initialization gesture; define a 3D interaction zone relative to the tracked motion of the part of the human hand visible in the sequence of frames of video data corresponding to the predetermined initialization gesture, where the 3D interaction zone corresponds to a bounded region that is less than the frame of video and that contains the part of the human hand visible in the sequence of frames of video data; and commence tracking the human hand within the 3D interaction zone as part of a gesture based interactive session by performing a search restricted to the bounded region corresponding to the 3D interaction zone in a sequence of frames of video data for a grouping of pixels that have image gradient orientations that match the edge features of one of the plurality of edge feature templates.