. Material appearance such as that of leather is usually reproduced with microfacet models in computer graphics. A more realistic result is achieved by adding a thin-film coating that produces iridescent colors [Akin 2014] . We replace the classic Fresnel reflectance term with a new Airy reflectance term that accounts for iridescence due to thin-film interference. Our main contribution consists in an analytical integration of the high-frequency spectral oscillations exhibited by Airy reflectance, which is essential for practical rendering in RGB. For the leather material on the model, we used a thin film of index η 2 = 1.3 and thickness d = 290nm, over a rough dielectric base material (α = 0.2, η 3 = 1). When the scene is rotated, goniochromatic e ects such as subtle purple colors may be observed at grazing angles. In this work, we introduce an extension to microfacet theory for the rendering of iridescent e ects caused by thin-lms of varying thickness (such as oil, grease, alcohols, etc) on top of an arbitrarily rough base layer. Our material model is the rst to produce a consistent appearance between tristimulus (e.g., RGB) and spectral rendering engines by analytically pre-integrating its spectral response. The proposed extension works with any microfacet-based model: not only on re ection over dielectrics or conductors, but also on transmission through dielectrics. We adapt its evaluation to work in multiscale rendering contexts, and we expose parameters enabling artistic control over iridescent appearance. The overhead compared to using the classic Fresnel re ectance or transmittance terms remains reasonable enough for practical uses in production.
Lately, REF extended microfacet-based models to recreate thin-film interference.
A practical extension to microfacet theory for the modeling of varying iridescence
TOGS
Mathematics Computer Science