Comparison of the Results of Modeling a Dispersed Medium by Wave and Ray Methods

Abstract

A large number of works on dispersed medium modeling use either pure ray optics or light transport equation in which propagation of light obeys geometric optics while scattering properties of the medium can be either calculated with wave optics or measured. In either case the distance between individual particles must be much greater than wavelength. At the same time current computer power allows to simulate paint layer with wave optics. We decided to compare paint simulation done by the scalar wave approach and by ray tracing with individual particles. One of the goals of this work is to verify the correctness of ray tracing results for various sizes of metal flakes used often in production of metallic or pearlescent paints. Ray tracing had been done in two variants. One assumes the flakes have perfectly mirror reflection, while in the other variant the reflection is slightly diffuse with the angular distribution taken from the Fraunhofer diffraction on thin disk. For not too large flakes results of these two approaches substantially differ. The second “hybrid” method is considerably closer to the wave optics results.