1. A computer system comprising: a processing device, and a memory device storing computer-executable instructions which, when executed by the processing device, cause the processing device to: extract a plurality of features from a plurality of images assigned to a plurality of material categories, wherein the plurality of features comprises at least one reflectance-based feature and at least one non-reflectance based feature; and select a subset of the plurality of features, wherein the subset of the plurality of features is selected by a learning procedure in which combinations of features are analyzed to determine the subset of the plurality of features, wherein the learning procedure is a greedy algorithm that considers contributions of each of the plurality of features in a stepwise manner.