A New Ward BRDF Model with Bounded Albedo

Abstract

Due to its realistic appearance, computational convenience, and efficient Monte Carlo sampling, Ward s anisotropic BRDF is widely used in computer graphics for modeling specular reflection. Incorporating the criticism that the Ward and the Ward-Duer model do not meet energy balance at grazing angles, we propose a modified BRDF that is energy conserving and preserves Helmholtz reciprocity. The new BRDF is computationally cheap to evaluate, admits efficient importance sampling, and thus sustains the main benefits of the Ward model. We show that the proposed BRDF is better suited for fitting measured reflectance data of a linoleum floor used in a real-world building than the Ward and the Ward-Duer model.