A simple layered RGB BRDF model

Many natural objects, and general layered materials, have non-linear reflection behaviour along wavelengths. An accurate representation of phenomena such as interference and colour separation generally requires a fine spectral representation of light instead of the commonly used RGB components. In this article, we introduce and experiment with a general approach to create similar and convincing effects, with a simple RGB BRDF model. We present a model for both specular and diffuse reflection.