1. A method comprising: assigning one or more samples to a plurality of clusters, each cluster in the plurality of clusters corresponding to an aggregate stored in an aggregate geometry buffer, wherein each of the one or more samples is covered by a visible fragment; rasterizing three-dimensional geometry to generate material parameters for each sample of the one or more samples; for each cluster in the plurality of clusters, combining the material parameters for each sample assigned to the cluster to produce the aggregate; and storing the combined material parameters for each cluster in the aggregate geometry buffer.