1. A method of processing data defining a plurality of depth maps of a subject object, to generate a 3D computer model of the subject object comprising points in a three-dimensional space representing points on the surface of the subject object, the method comprising: processing each depth map to connect points therein to generate a respective two-dimensional mesh of connected points in each depth map; projecting each two-dimensional mesh into three-dimensional space in dependence upon the position and orientation in the three-dimensional space of the depth map containing the mesh and the respective depths of the points in the mesh defined by the depth map, to generate a respective polyhedron from each depth map, each polyhedron comprising a three-dimensional mesh of connected vertices defining planar faces corresponding to the two-dimensional mesh, together with planar side faces for each edge of the three-dimensional mesh; calculating points in the three-dimensional space representing points on the surface of the subject object by calculating the respective points at which a predetermined number of the planar surfaces from the generated polyhedra intersect.