Modeling pigmented materials for realistic image synthesis

Reviewer: Adina Raclariu

The Kubelka-Munk theory of pigment mixing is described and applied to computer graphics as a solution for improving image synthesis. The superiority of Kubelka-Munk theory is discussed in the case of pigmented surfaces, which have both transmitting and reflecting characteristics. Pigment mixing is an example of an optical phenomenon that can be modeled if the spectral energy distributions of the light sources in the environment are given and the spectral reflectance, transmittance, and absorptance of the surface with which these light sources interact are specified. Pigmented solutions, which consist of opaque particles in a transparent medium, are quite different from the completely transparent solutions of subtractive colorants. To understand pigmented solutions, one must study them on a particle level, which has both absorbing and reflecting properties. This level of detail is too complex for calculating information about pigment solutions, however. The Kubelka-Munk method is the only way to include the absorption and scattering phenomena that take place in real paint films. The paper offers a solution to the matching problem of interpreting the user's intuitive color designation and then producing a pigment specification. This original solution takes metamerism into account. (Metamers are spectral energy distributions that look the same to the human eye.) This approach to color matching has two major advantages over the standard color matching techniques covered in the references. The obtained results are the closest color match in terms of a color difference formula, and the formula used admits an arbitrary number of pigments and attempts to find a suitable match from that set, regardless of how many pigments are to be used. The purpose of this work is to demonstrate the capabilities of realistic pigment modeling in computer graphics. The importance of computer graphics in the pigment industry is outlined.