1. A method of tracking parameters of an entity comprising: receiving raw image data depicting the entity from a time of flight camera; accessing a 3D model of the entity, the 3D model having model parameters; rendering, from the 3D model having specified values of the model parameters, simulations of raw time of flight image data depicting the entity; comparing the simulated raw image data and at least part of the received raw image data; calculating, on the basis of the comparison, values of the tracked parameters of the entity.