Talk by Sebastien Hillaire at SIGGRAPH 2015 in the Advances in Real-time Rendering course.
Rendering convincing participating media for real time applications, e.g. games, has always been a difficult problem. Particles are often used as a fast approximation for local effects such as dust behind cars or explosions. Additionally, large scale participating media such as depth fog are usually achieved with simple post-process techniques. It is difficult to have all these elements efficiently interacting with each other according to the lights in the scene.
The authors propose a way to unify these different volumetric representations using physically based parameters: a cascaded volume representing extinction, voxelization method to project particles into that extinction volume, a simple volumetric shadow map that can then be used to cast shadow from any light, according to every volumetric element in the scene, and finally a solution to render the final participating media.
The presented set of techniques and optimizations form the physically based volumetric rendering framework that will be used for all games powered by Frostbite in the future.