1. A method of processing vertex data, the method comprising: with a vertex shader, receiving vertex data for a plurality of vertices; identifying a first subset of the plurality of vertices having at least one type of symmetry relationship of a number of types of symmetry relationships to one or more other subsets of the plurality of vertices; creating a set of control data including information identifying the at least one type of symmetry relationship for reconstructing at least a part of the one or more other subsets using vertex data for the first subset; and with a geometry shader, computing additional vertices using the control data and the vertex data for the first subset to thereby reconstruct at least a part of the one or more other subsets.