Acquisition and Analysis of Bispectral Bidirectional Reflectance and Reradiation Distribution Functions
In ﬂuorescent materials, light from a certain band of incident wavelengths is reradiated at longer wavelengths, i.e., with a reduced per-photon energy. While ﬂuorescent materials are common in everyday life, they have received little attention in computer graphics. Especially, no bidirectional reradiation measurements of ﬂuorescent materials have been available so far. In this paper, we extend the well-known concept of the bidirectional reﬂectance distribution function (BRDF) to account for energy transfer between wavelengths, resulting in a Bispectral Bidirectional Reﬂectance and Reradiation Distribution Function (bispectral BRRDF). Using a bidirectional and bispectral measurement setup, we acquire reﬂectance and reradiation data of a variety of ﬂuorescent materials, including vehicle paints, paper and fabric, and compare their renderings with RGB, RGB×RGB, and spectral BRDFs. Our acquisition is guided by a principal component analysis on complete bispectral data taken under a sparse set of angles. We show that in order to faithfully reproduce the full bispectral information for all other angles, only a very small number of wavelength pairs needs to be measured at a high angular resolution.
AddressDr. Ivo Ihrke
INRIA Bordeaux Sud-Ouest
200 avenue de la vieille tour
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