Degree of polarization modeling based on modified microfacet pBRDF model for material surface

The polarized bidirectional reflectance distribution function (pBRDF) can effectively simulate the degree of polarization (DoP) characteristics of material surface. Most of the existing pBRDF models include a Lambertian constant diffuse scattering component that the scattering and absorption of light inside the material is completely ignored. In this paper, a modified microfacet pBRDF model is proposed for material surface with considering specular reflection and diffuse scattering based on the combination of the microfacet and Kubelka-Munk (K-M) theory. In this model, a scaling parameter is introduced into specular reflection component to adjust the model which contains all the polarization information, and the diffuse scattering component is depolarization modeled following the K-M theory. The expression of DoP is developed from the new pBRDF model that includes the scattering and absorption effects in bulk of material, which makes more reasonable with physical interpretation. Several experiment groups of DoP for coating samples (rough yellow and black paint) are measured by the mull-angle polarization instrument, and then, the model parameters are fitted by least square method based on the experimental data. The results show that the DoP values calculated by the modified microfacet pBRDF model are found to be consistent with the measured DoP values, and can significantly improve the modeling accuracy, which provides theoretical support for polarization remote sensing and object recognition.