This page provides an overview of the atmospheric effects available in V-Ray for Houdini.
The atmospheric effects in V-Ray simulate fog and participating media for a number of image effects. These effects also include V-RayToon, a cartoon-styled non-photorealistic effect that enables toon shading as a render effect throughout the scene, and Volumetric Grid rendering that works with grid based cache formats to create effects such as dynamic plumes of smoke.
True atmospheric effects are applied throughout the entire scene as viewed from the viewport. While parameters give limited control over the appearance of the effect, atmospheric effects render faster than volumetric effects.
Volumetric effects use a volume to contain the atmospheric effect. While volumetric effects offer a great deal of control over the placement of the effect, they take longer to render.