1. A graphics processing unit comprising: a tiling unit configured to identify a plurality of primitives touching a corresponding tile of a plurality of tiles in an image frame, to determine at least one representative primitive of the plurality of primitives using a depth value of each of the plurality of primitives, and to determine visible primitives of the plurality of primitives for the corresponding tile using a depth value of the at least one representative primitive; and a rasterizer configured to rasterize the at least one representative primitive and the visible primitives for the corresponding tile, wherein the at least one representative primitive is rasterized prior to the visible primitives, and the visible primitives are rasterized according to a rendering order.