A Fresnel Model for Coated Materials

Abstract

We propose a novel analytical RGB model for rendering coated conductors, which provides improved accuracy of Fresnel reflectance in BRDFs. Our model targets real-time path tracing and approximates the Fresnel reflectance curves with noticeably more accuracy than Schlick's approximation using Lazanyi's error compensation term and the external media adjustment. We propose an analytical function with coefficients fitted to measured spectral datasets describing the complex index of refraction for conductors. We utilize second-order polynomials to fit the model, subsequently compressing the fitted coefficients to optimize memory requirements while maintaining quality. Both quantitative and visual results affirm the efficacy of our model in representing the Fresnel reflectance of the tested conductors.