λi λo Fluor. yellow Fluorescent red Green spraypaint Pink spraypaint Dullday-glo red White paper Figure 1: Fluorescent materials absorb part of the incoming light at wavelength λi and reradiate it at the longer wavelength λo. We have measured bispectral BRRDFs to capture such materials and render them in the spectral environment map of a winter sunset. The bottom row depicts slices of the bispectral BRRDF, showing one rendered sphere for each pair of incident and reflected or reradiated wavelengths (λo,λi) ∈ [400nm;720nm] ×[380nm;720nm]. Fluorescence isrepresented bythe off-diagonal entries. Influorescentmaterials,lightfromacertainbandofincidentwavelengths 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, includingvehiclepaints,paperandfabric,andcomparetheirrenderings with RGB, RGB×RGB, and spectral BRDFs. Our acquisition isguidedbyaprincipalcomponentanalysisoncompletebispectral 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 atahigh angular resolution
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.