A General Micro-flake Model for Predicting the Appearance of Car Paint

Abstract

We present an approximate model for predicting the appearance of car paint from its paint composition. Representing the appearance of car paint is not trivial because of its layered structure which is composed of anisotropic scattering media. The Radiative Transfer Equation (RTE) is commonly used to represent the multiple scattering for the underlying structures. A number of techniques including the Monte Carlo approach, the discrete ordinates, the adding-doubling method, the Eddington approximation, as well as the 2-stream and diffusion approximations have been proposed so far to improve visualization accuracy. Each of these techniques hold advantages over the others when their appropriate conditions are met. The adding-doubling method, in particular, is recognized to be computationally simple and accurate. Jakob et al. [JAM 10] has generalized the RTE for anisotropic scattering structures and proposed to use a micro-flake model based on double-sided specularly reflecting flakes. They also developed an anisotropic diffusion approximation to solve the corresponding RTE. In this paper, considering the translucent micro-flakes we proposed to use a modified version of the model which was developed by Jakob et al. We utilized the adding-doubling method instead of the diffusion-approximation for the new micro-flake model. The proposed approach also provided a good ground for data compression used in the evaluation of RTE. Empirical comparisons have been made to assess the accuracy and computational efficiency of the proposed model. Based on the sample data, we showed that our model provides visually satisfactory results for the appearance of multi-layered car paint.