We describe light reflection models adequate for generating realistic images of reflective object surfaces. The surface-spectral reflectance of an object varies with the geometry of illumination and viewing. This function also depends on the object's material composition. First we show three types of dichromatic reflection models for describing surface-spectral reflectances of a variety of materials. The Type I model for inhomogeneous dielectric materials, such as plastics, assumes that surface reflection consists of two additive components, the body reflection and the interface reflection that is independent of wavelength. The Type II model for cloths and papers allows wavelength-dependent interface reflection. The Type III model for metals has two interface reflection components. Next we determine the geometric factors of illumination and viewing angles, which so far had been left as undetermined weighting coefficients to the spectral components. The intensity distribution of the reflected light from a surface is formulated by referring to reflection models in computer graphics. Thus, reflective object surfaces of most materials can be rendered using these three types of dichromatic models. Finally, sample images for different surface types are generated.
Shoji Tominaga, "Dichromatic Reflection Models for Rendering Object Surfaces" in Journal of Imaging Science and Technology, 1996, pp 549 - 555, https://doi.org/10.2352/J.ImagingSci.Technol.1996.40.6.art00011