A Simple Diffuse Fluorescent BBRRDF Model

Alisa Jung, Johannes Hanika, Steve Marschner, and Carsten Dachsbacher

EG Digital Library (MAM 2018: Eurographics Workshop on Material Appearance Modeling)

A fluorescent and non-fluorescent sphere with the same base reflectance, and their RGB-space blue channels (lower triangles) with increased exposure. The fluorescent sphere’s blue channel is in fact negative. Fluorescence can produce saturations that cannot be captured in RGB, like the values of the dotted square (right plot). Even a spectral renderer would only be able to produce such saturations at the cost of a lower brightness. The absorption and emission spectra (fluorescein) of the left sphere and the non-fluorescent reflectance spectrum (color checker green) of both spheres are shown second to right.


Fluorescence — the effect of a photon being absorbed at one wavelength and re-emitted at another — is present in many common materials such as clothes and paper. Yet there has been little research in rendering or modeling fluorescent surfaces. We discuss the design decisions leading to a simple model for a diffuse fluorescent BBRRDF (bispectral bidirectional reflection and reradiation distribution function). In contrast to reradiation matrix based models our model is continuous in wavelength space. It can be parameterized by artificially designed spectra as well as by many publicly available physical measurements. It combines fluorescence and non-fluorescent reflectance, as most real- world materials are not purely fluorescent but also reflect some light without changing its wavelength. With its simple parameterization the BBRRDF is intended as a starting point for any physically based spectral rendering system aiming to simulate fluorescence. To that end we show how to continuously sample both incident and exitant wavelengths from our BBRRDF which makes it suitable for bidirectional transport, and we discuss energy and photon conservation in the context of fluorescence.





  @inproceedings {m.20181193,
booktitle = {Workshop on Material Appearance Modeling},
editor = {Reinhard Klein and Holly Rushmeier},
title = {{A Simple Diffuse Fluorescent BBRRDF Model}},
author = {Jung, Alisa and Hanika, Johannes and Marschner, Steve and Dachsbacher, Carsten},
year = {2018},
publisher = {The Eurographics Association},
ISSN = {2309-5059},
ISBN = {978-3-03868-055-0},
DOI = {10.2312/mam.20181193}