A surface model is generated from a three-dimensional volume model of a person's head. The person's head is modelled as a three-dimensional volume model of loss values (i.e., absorption values). Wave vectors are launched towards the volume model. Each wave vector is characterized by a wavelength and a capture direction (direction of propagation). The launched wave vectors are absorbed by the volume and the point at which they are absorbed (referred to as the intersection point) is determined. The surface model of the person's head is generated from the intersection points of the wave vectors.