1. A method of rendering graphics with a processing unit, the method comprising: determining a sample coverage of a first primitive at a first pixel, wherein the first pixel includes a plurality of samples, wherein the plurality of samples include one or more color samples and a plurality of depth samples, wherein it is determined in said determining the sample coverage that the plurality of samples of the first pixel include one or more covered samples that are covered by the first primitive; determining whether the one or more covered samples include at least one of the color samples of the first pixel; invoking a pixel shader for the first pixel for the first primitive if said determining determines that the one or more covered samples include at least one of the color samples; and not invoking the pixel shader for the first pixel for the first primitive if said determining determines that the one or more covered samples do not include at least one of the one or more color samples but do include at least one depth sample of the plurality of depth samples; deriving a color value, for the first primitive, for a display pixel not associated with a color sample but associated with a depth sample by assigning a color value of a color sample at a same depth value as the depth sample.