A Survey of BSDF Measurements and Representations (original) (raw)

Grand Challenges in BSDF Measurement and Modeling

Measuring and representing reflection and transmission accurately are core to high fidelity visual simulation of materials. However, state-of-the-art Bidirectional Scattering Distribution Function (BSDF) models do not suggest a general solution for any surface class, from glasses to metals, isotropic to anisotropic materials, and daylight redirecting films. Furthermore, an accurate BSDF acquisition is not a trivial task at especially some specific measurement angles, such as normal incidence and grazing angles. In this paper, we address the problem of finding a general solution for efficient BSDF measurement and representation. We also outline the main issues that do not allow the effective use of current BSDF representations. Finally, we suggest specific solutions that could be investigated in order to address these challenges.

Experimental Analysis of BSDF Models

The Bidirectional Scattering Distribution Function (BSDF) describes the appearance of an optically thin, translucent material by its interaction with light at a surface point. Various BSDF models have been proposed to represent BSDFs. In this paper, we experimentally analyze a few of BSDF models in terms of their accuracy to represent measured BSDFs, their required storage sizes and computation times. To make a fair comparison of BSDF models, we measured three samples of optically thin, translucent materials (hunter douglas, orange glass, structured glass) by using pgII gonio-photometer. Based on rendered images, required storage sizes and computation times, we compare the performance of the BSDF models. We show that data-driven BSDF models give a more accurate representation of measured BSDFs, while data-driven BSDF models require much more storage sizes and computation times. We also show that BSDF measurements from highly anisotropic translucent materials can not be expressed by an analytical BSDF model visually correctly.

Reducing Anisotropic BSDF Measurement to Common Practice

We address the problem of measuring and representing reflection and transmission for anisotropic materials without relying on mathematical models or a large sample database. By eliminating assumptions of material behavior, we arrive at a general method that works for any surface class, from metals to fabrics, fritted glazing, and prismatic films. To make data gathering practical, we introduce a robust analysis method that interpolates a sparse set of incident angle measurements to obtain a continuous function over the full 4-D domain. We then convert this interpolant to a standard representation tailored for efficient rendering and supported by a common library that facilitates data sharing. We conclude with some remaining challenges to making anisotropic BSDF measurements truly practical for rendering.