ABSTRACT
In this chapter, the authors present a new method for rendering realistic clouds. The key idea of their approach is to precompute optical depth and single and multiple scattering for a reference particle at preprocess time and to store the resulting information in lookup tables. Rendering realistic clouds has always been a desired feature for a variety of applications, from computer games to flight simulators. Clouds consist of innumerable tiny water droplets that scatter light. The authors present a new physically based method to efficiently render realistic animated clouds. The authors produce two main simplifications when approximating shading: scattering is precomputed in a homogeneous spherical particle, and energy exchange between particles is ignored. They address the main concepts of the light transport in a participating medium. The authors utilize the value on the particle surface to compute attenuation for multiple scattering and the value in the particle center for single scattering.
