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Proceedings Paper

Algorithmic model of microfacet BRDF for Monte Carlo calculation of optical radiation transfer
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Paper Abstract

An algorithmic model of bi-directional reflectance distribution function (BRDF) based on the ray optics approximation and microfacet model of randomly rough surface is proposed. Its central idea is that for every incident ray, the normal vector to the surface undergoes a random perturbation, and the direction of specular reflection is calculated using this perturbed normal. Such behavior of the normal can be treated within the framework of a microfacet model of randomly rough surfaces. The algorithm allows one to model reflection from both isotropic and anisotropic surfaces, with two-dimensional Gaussian and other probability density functions for the normal vector perturbations, and various geometrical attenuation functions. The proposed "perturbed normal microfacet (PNMF) model" exhibits experimentally observed effects such as increased reflectance near grazing incidence and off-specular peaks, and allows fast importance sampling. A weighted sum of Lambertian and PNMF BRDFs can be fitted to experimental data by varying the appropriate parameters. Adherence to the reciprocity principle and energy conservation law is demonstrated via results of forward and backward ray tracing. The PNMF model can be used in Monte Carlo calculations of radiative heat exchange among rough surfaces, in realistic image synthesis, lighting engineering, for modeling of such radiometric devices as blackbody radiation sources, integrating spheres in the infrared spectral range, cavity detectors of radiation, diffusely reflected panels, etc.

Paper Details

Date Published: 14 November 2003
PDF: 17 pages
Proc. SPIE 5192, Optical Diagnostic Methods for Inorganic Materials III, (14 November 2003); doi: 10.1117/12.508577
Show Author Affiliations
Alexander V. Prokhorov, National Institute of Standards and Technology (United States)
Leonard M. Hanssen, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 5192:
Optical Diagnostic Methods for Inorganic Materials III
Leonard M. Hanssen, Editor(s)

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