This disclosure describes techniques for rendering pixels on a display. A processing unit may receive pixel values for surface pixels of each surface of a plurality of surface. The processing unit may also receive an order of the plurality of surfaces. Based on at least the location and order of the plurality surfaces, the processing unit may blend pixel values for co-located surface pixels. The processing unit may also accumulate opaqueness values for co-located surface pixels and/or opaqueness values for surfaces with co-located surface pixels.