One or more pull force vectors are applied to one or more force receiving locations of the model to pull the model in an XY plane towards the silhouette of the human target in the observed depth image when {HEAD ~ portions} of the observed depth image are shifted away from the silhouette of {TAIL ~ the model} 
One or more pull force vectors are applied to one or more force receiving locations of the model to pull the model in an XY plane towards the silhouette of the human target in the observed depth image when { HEAD ~ portions } of the observed depth image are shifted away from the silhouette of { TAIL ~ the model }
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