Multiple scattering is a crucial part of photorealistic rendering of high-albedo media. In order to convincingly render optically thick media with multiple scattering effects, high scatter orders must be included, upwards of one hundred bounces. We have found that changing the amount of diffusion in a cloud greatly impacts the perceived scale of the scene, but that contrast can be adjusted substantially to suit the image without compromising scale. With this distinction in mind, we developed a method that computes efficient and physically accurate diffusion, but that allows independent control over contrast.
