1. A 3-D rendering system, comprising: a tiling unit configured to produce a respective object list for each tile of pixels within a frame of pixels to be rendered that is divided into a plurality of tiles, each object list identifying geometry elements that overlap its tile; a rasterizer comprising a fetch unit, coupled to a memory for storing untransformed data for geometry elements to be used in rendering; a transform unit coupled with the fetch unit, and operable to produce transformed data for a geometry element from received untransformed data from the fetch unit; a cache; a cache controller coupled with the cache, the cache controller operable to receive the transformed data and control storage of the transformed data in the cache; and a hidden surface removal unit operable to process an object list for a tile by receiving transformed data from the cache if present, for a geometry element identified in the object list for the tile, wherein the system is configured to arrange for the retrieval of untransformed data for a geometry element identified in the object list for provision to the transform unit to produce said transformed data, said transformed data being provided for usage by the hidden surface removal unit and cached in the cache for possible subsequent use.