Environment Object
Use the Environment object to define several global scene parameters such as the scene's environment light (also known as ambient lighting).
By default, only the top-most Environment object in the hierarchy will be rendered. If you want to change the environment during an animation, use the Stage object with a parameter track.
You can use the Environment object with volumetric shaders. Plug-ins or the optional PyroCluster can be used in this way to create effects such as smoke and fog. Simply apply the shader to the Environment object as a texture.