This demos shows volumetric smoke using a particle system, a GLSL sky shader and simple atmospheric scattering using GLSL shaders.
The smoke is rendered using a particle system with billboarded quads. To make the animation more dynamic, each particle is influenced by vortex particles. The demo also features a GLSL sky shader which allows you to adjust the cloud cover and cloud sharpness. Of course, per-pixel lighting and PCF Soft Shadows are also featured.
Download Volumetric Smoke Demo (~7MB)