1. A method of processing geometry for 3-D graphics rendering, comprising: distributing a stream of scene geometry data, describing elements of scene geometry, among a plurality of geometry processing units, wherein the distributing is according to a predefined convention; in each of the geometry processing units, maintaining one respective tile reference list containing a series of entries that each identify an element of scene geometry processed by that geometry processing unit, and one or more screen-space tiles, of a plurality of screen-space tiles, that the element of scene geometry overlaps, and for each tile that the element of scene geometry overlaps, a pointer to parameter information for the element within a tiled geometry list produced by that geometry processing unit; and in a tile list builder shared among the geometry processing units, reading entries from each of the tile reference lists from the plurality of geometry processing units in an order determined by the predefined convention, producing a master tile list comprising, for each screen-space tile overlapped by at least one of the elements of scene geometry, a respective list of the pointers obtained from the tile reference lists maintained by the geometry processing units that point to respective parameter information for the elements of scene geometry overlapping that screen-space tile.