A Model for Anisotropic Reflection
Pierre
Poulin and Alain
Fournier
Proc. SIGGRAPH, August 1990
Abstract
A reflection and refraction model for anisotropic surfaces
is introduced. The anisotropy is simulated by small cylinders (added or
subtracted) distributed on the anisotropic surface. Different levels of
anisotropy are achieved by varying the distance between each cylinder and/or
rising the cylinders more or less from the surface. Multidirectional anisotropy
is modelled by orienting groups of cylinders in different direction. The
intensity of the reflected light is computed by determining the visible
and illuminated portion of the cylinders, taking self-blocking into account.
We present two techniques to compute this in practice. In one the intensity
is computed by sampling the surface of the cylinders. The other is an analytic
solution. In the case of the diffuse component, the solution is exact.
In the case of the specular component, an approximation is developed using
a Chebyshev polynomial approximation of the specular term, and integrating
the polynomial.
This model can be implemented easily within most rendering system,
given a suitable mechanism to define and alter surface tangents. The effectiveness
of the model and the visual importance of anisotropy are illustrated with
some pictures.
BibTeX entry
@Article{Poulin:1990:MAR,
author = "Pierre Poulin and Alain Fournier",
editor = "Forest Baskett",
title = "A Model for Anisotropic Reflection",
journal = "Computer Graphics",
volume = "24",
number = "4",
pages = "273--282",
month = aug,
year = "1990",
coden = "CGRADI, CPGPBZ",
ISSN = "0097-8930",
conference = "held in Dallas, Texas; 6--10 August 1990",
keywords = "shadowing, surface mapping, Chebyshev polynomials,
hair rendering, scientific visualization",
}
Online Version
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