Maya’s volumetric materials and mental ray for Maya’s volumetric materials let you simulate fog, smoke, dust, or other atmospheric effects.

You can create atmospheric effects such as fog, smoke, dust in the following ways:

• For basic spherical, conical or cubicle effects, create the appropriate Maya volume primitive, then assign a Maya volumetric material to it, then render with Maya software.
• For more complex shapes, create any geometrical object, then assign a Maya volumetric material to it, then render with mental ray for Maya.
• Use mental ray for Maya’s participating media. The workflow involves assigning a transfer material to achieve physically accurate light participation, with the potential to generate shadows and caustics.

(Alternatively, you can create the effect in post production (that is, outside Maya).)