1. A system for rendering an image made up of primitive elements that are defined by a plurality of vertices the system having: a vertex storage area holding vertex information for each vertex addressable by a vertex index; an index processing unit for generating from said vertex indices a set of unique indices identifying a batch of vertices; and a graphics functional unit arranged to load into the vertex storage area only the vertices associated with said generated set of unique indices and operable to transform vertices in said batch to create transformed primitive elements using the set of unique indices to address the vertex storage area.