The paper introduces a method, called the albedo pumping-up, to derive new, physically plausible BRDFs from an existing one or from any symmetric function. This operation can be applied recursively by arbitrary number of times. An important application of this operation is the transformation of the Phong and Blinn models in order to make them produce metallic effects. The paper also examines the albedo function of reflectance models and comes to the conclusion that widely used models violate energy balance at grazing angles.
Reflectance function, BRDF representation, albedo function, energy balance,
metal models, perceptual based fitting}