Modernizing the Disney BRDF Viewer

Abstract

In this work, a new layered BRDF explorer is presented. This BRDF explorer allows users to create and visualize layered material models consisting of analytical BRDFs and, as planned feature, measured BRDFs. The need for a new layered BRDF explorer comes from the fact that previous software has become outdated, the fact that the plotting of PDFs is often not supported, and the fact that visualization of BRDF response is useful due to the high dimensionality of BRDF data. The effect of importance sampling techniques on render quality and convergence is inves- tigated within the context of layered material models. Visual differences due to the choice of layered material model and choice of importance sampling technique are investigated using statistical methods using a difference evaluator (NVIDIAF LIP). An error of 0.11% was found for a two-layer BRDF stack when rendering with Multiple Importance Sampling enabled compared to the original Weidlich-Wilkie layered material model. This error indicates a bias in the sampling method affecting convergence. Variance during rendering is slightly reduced however when using Multiple Importance Sampling. A BRDF explorer software package that supports rendering with layered materials is also provided along with this work.