A Practical Extension to Microfacet Theory for the Modeling of Varying Iridescence

摘要

In this work, we introduce an extension to microfacet theory for the rendering of iridescent eu001dects caused by thin-films of varying thickness (such as oil, grease, alcohols, etc) on top of an arbitrarily rough base layer. Our material model is the first 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 reu001eection 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 reu001eectance or transmittance terms remains reasonable enough for practical uses in production.