Interference shader for multilayer films

Abstract

To visualize the interference effects of objects with multilayer film structures such as soap bubbles, optical lenses and Morpho butterflies is challenging and valuable in the physics-based framework, a novel multilayer film interference shader is constructed. The multibeam interference equation is applied to effectively simulate the multiple reflection and transmission inside films, and calculate the composite reflectance and transmittance to model the amplitude and phase variations related to interference. The absorption of photons due to the film materials is accounted for by the Fresnel coefficients used for metallic and dielectric films. In addition, the irregularity of multilayer film microstructures is incorporated into the iridescent illumination model to explain the isotropic and anisotropic optical properties. The new wave bidirectional scattering distribution function is proposed and integrated into the existing ray tracer in the form of the material plugin to further enhance the photorealistically rendering capabilities. The experiments show that our interference shader gives accurate results in both visual and numerical quality.