1. A method for tracking a user, the method comprising: receiving a depth image; generating a first voxel of a plurality of voxels based on at least one pixel of the depth image that corresponds to a background independent of at least one pixel that corresponds to a human target, the first voxel overlapping another voxel in the plurality of voxels; removing the first voxel from the plurality of voxels to isolate one or more voxels associated with the human target; determining a location or position of one or more extremities of the human target based on the one or more voxels associated with the human target; and adjusting a model based on the location or position of the one or more extremities.