1. A method for use with depth images, comprising: obtaining a depth image and information that specifies that a subset of pixels within the depth image correspond to a user; transforming pixels in the depth image from depth image space to three-dimensional (3D) camera space to produce a 3D representation of the depth image in the 3D camera space which includes a subset of pixels in the 3D camera space specified as corresponding to the user; after the transforming, identifying one or more pixels in the 3D camera space, of the subset of pixels in the 3D camera space specified as corresponding to the user, that likely correspond to a floor that is supporting the user; removing, from the subset of pixels in the 3D camera space specified as corresponding to the user, the one or more pixels in the 3D camera space identified as likely corresponding to the floor that is supporting the user; and after the removing, transforming the 3D representation of the depth image from the 3D camera space back to the depth image space.