Seeing Beyond Lambert's Law

Lambert's model for diiuse reeection is extensively used in computational vision. For several real-world objects, the Lambertian model can prove to be a very inaccurate approximation to the diiuse component. While the brightness of a Lambertian surface is independent of viewing direction, the brightness of a rough diiuse surface increases as the viewer approaches the source direction. A comprehensive model is developed that predicts reeectance from rough diiuse surfaces. Experiments have been conducted on real samples, such as, plaster, clay, and sand. The reeectance measurements obtained are in strong agreement with the reeectance predicted by the proposed model.