A generalized BRDF model for data fitting

Abstract

This paper aims to reproduce several types of cloth using the data fitting method. A generalized framework was developed for data fitting and its extension to different types of cloth. To make visually natural cloth in computer graphics, the reflective properties of cloth material must be well understood. Bidirectional Reflectance Distribution Function(BRDF) is the most commonly used function to describe the light reflection of a specific material. The BRDF model used in this paper is microfacet based, as most physically based BRDF models are based on microfacet theory. In microfacet theory, microfacets normal direction has the highest probability to be their surface normal direction. In this paper, we change the orientation of microfacet distribution, and use this modified microfacet distribution function for data fitting. As multiple specular lobes are used in data fitting for isotropic materials, we use multiple specular lobes in anisotropic materials with different orientations. During the data fitting procedure, we acquire the specular and diffuse term separately for efficiency.