Oren–Nayar reflectance model

The Oren–Nayar reflectance model is a widely used model in computer graphics that describes how light reflects off rough surfaces. It was introduced by Oren and Nayar in 1994 as an improvement over the traditional Lambertian reflectance model, which assumes perfectly diffuse reflection. The Lambertian model is straightforward and works well for smooth surfaces, but it fails to accurately represent the complex interaction of light with rough surfaces that have microfacets.