Yes you heard that correctly…Unity has a layering system for lighting! If you have an object that you want to receive lighting without that light source casting light on the entire environment, then you have come to the right place my friend!
Let’s get started by placing a spotlight outside where it’s nice and foggy. The amazing Area Lights will not currently work with this, but a spotlight or point light will do just fine.
Your light as well as your fog need to have volumetric features enabled. If you have already done this and you can’t see the fog in the light source, try increasing the value on the Volumetric Fog Distance.
You can see that as I increase the distance, the fog now appears more readily in the light and less in the environment.
Now the fog receives more light from the source, as would be true in a real life environment.
Changing the Temperature of the light source has a large impact on the fog itself.
You might notice some pixelation when moving the light around the scene.
Click the gear box icon on the Fog to reveal some additional options.