You create illuminated fog by adding it to an existing light.
Note:
To create fog that fills the entire scene, not just within the illumination of a specific light, use the Environment Fog Volumetric material. See Environment Fog.
To add illuminated fog to a light
- Select the light for which you want to illuminate fog.
- In the Light Effects section of the light’s Attribute Editor, click the map button beside the Light Fog attribute.
Maya automatically creates a light fog node, connects it to the light node, and displays its Attribute Editor.