DICHROMATIC REFLECTION MODELS FOR A VARIETY OF MATERIALS

This article proposes dichromatic reflection models adequate for describing surface-spectral reflectances of a variety of materials. The standard dichromatic reflection model for inhomogeneous materials assumes that light reflected from an object's surface is decomposed into two additive components: the body reflection and the interface reflection, which is independent of wavelength. First, we present a method for testing the adequacy of this standard model based on the observations of surface-spectral reflectances. The standard dichromatic reflection model is adequate for many materials. However, the test results point out that there are some cloths for which the standard model is inadequate, and metals that have only the interface reflection. Next, we extend the standard model to have an interface reflection component that depends on wavelength. An algorithm is presented for estimating two reflectance functions in the generalized model. Moreover, a dichromatic reflection model specialized for only the specular reflection is defined for approximating metal's reflection. The reflection characteristics are analyzed using a chromaticity diagram. It is concluded that surface spectral reflectances of most materials are described by three types of the dichromatic reflection model. (C) 1994 John Wiley & Sons, Inc.