1. A method for tracking a user comprising: receiving a depth image that was captured by a depth camera; identifying an estimated location or position of a part of the user in the depth image; adjusting a model of the user based on the estimated location or position of the part of the user; and in response to a failure to identify a location or position of the part of the user in a second depth image, adjusting the model to move the location or position of the part of the user in the model to a default position of the part of the user.
12. The method of claim 1 , further comprising: downsampling the pixels in the depth image before identifying the estimated location or position of the extremity of the user.