Due to illumination variability, the same object can appear dramatically different even when viewed in fixed pose. To handle this variability, an object recognition system must employ a representation that is either invariant to, or models this variability. This paper presents an appearance-based method for modeling the variability due to illumination in the images of objects. The method differs from past appearance-based methods, however, in that a small set of training images is used to generate a representation -- the illumination cone -- which models the complete set of images of an object with Lambertian reflectance under an arbitrary combination of point light sources at infinity. This method is both an implementation and extension (an extension in that it models cast shadows) of the illumination cone representation proposed in . The method is tested on a database of 660 images of 10 faces, and the results exceed those of popular existing methods. 1 Introduction An object's..