<title>Bidirectional reflectance from pigmented coatings</title>

Abstract

There has been increasing interest in the measurement, validation, and parameterization of the bidirectional reflectance distribution function (BRDF) from surface coatings for image simulation and rendering, and design models of coating systems. The complexity of data required depends on the finish or final appearance of the surface coating. In particular the development of optical effect pigments places heightened requirements on the BRDF data needed for adequate characterization of a surface coating. Measurements of the BRDF are presented from pigmented films representative of the top layer of a paint coating. The measurements investigate the scattering characteristics of pearlescent pigments as a function of the incident polar angle and the polar and azimuthal scatter angles, including a study of the spectral variation of the BRDF across the visible waveband from 350 nm to 800 nm. In addition, measurements of linearly polarized BRDF as a function of incident and reflected directions are reported. The measurements emphasize the various optical properties of coatings such as surface and volume scattering and polarization contributions, which need to be considered if the data is to be accurately modelled or parameterized and used effectively.