Recovering Illumination and Texture Using Ratio Images

In this paper we consider the problem of factoring illumination and texture from a pair of images of a diffuse object of known geometry. This problem arises frequently in 3D photography applications that use images to acquire photometric properties of a scanned object. Our approach uses the ratio of the images and the geometry information to compute the relative incident irradiance of one image with respect to the other. After the irradiance maps are recovered, we build a spatially varying albedo map, which can then be used to render the object under different illumination conditions. We present two algorithms, one for point-light source illumination, and another one based on spherical harmonics for more general illumination conditions.