Spatial errors identifying differences between spatial co-ordinates of vertices of a mesh surface defined by mesh data and corresponding vertices in a mesh surface generated from an encoded representation of the mesh data are determined. The carbon is derived from metal or metalloid carbides. The first and the second ceramic layer each have a sintering start temperature and a sintering end temperature, and at least one of the sintering start temperature and the sintering end temperature is different between the first and the second ceramic layer. A first one of such chassis includes a memory and a plurality of directors.