1. A method for processing data, comprising: receiving a depth map of a scene containing at least an upper body of a humanoid form, the depth map comprising a matrix of pixels having respective pixel depth values; using a digital processor, processing the depth map so as to identify a head and at least one arm of the humanoid form in the depth map; and based on the identified head and at least one arm, and without reference to a lower body of the humanoid form, extracting from the depth map an upper-body pose comprising at least three-dimensional (3D) coordinates of shoulder joints of the humanoid form.