1. A method comprising: receiving a depth image of a scene; determining that a portion of a human target in the depth image is non-visible; estimating a position of the non-visible portion of the human target, wherein the estimating comprises: generating an initial estimation of the position of the non-visible portion of the human target based at least in part on force vectors associated with a visible portion of the human target; and modifying the initial estimation based at least in part on historical data associated with the non-visible portion, wherein the historical data comprises data associated with a previously received depth image where the non-visible portion is visible, wherein the historical data comprises at least one of an X value, a Y value, or a Z value of the non-visible portion in the previously received depth image where the non-visible portion is visible; determining a new position of the non-visible portion when a pixel associated with the non-visible portion becomes visible in a subsequent depth image.