In accordance with some embodiments, a tile shader executes on a group of pixels prior to a pixel shader. The tile of pixels may be rectangular in some embodiments. The tile may be executed hierarchically, refining each tile into smaller subtiles until the pixel or sample level is reached. The tile shader program can be written to discard groups of pixels, thereby quickly removing areas of the bounding triangles that lie outside the shape being rasterized or quickly discarding groups of pixel shader executions that will not contribute to the final image.