Below is a simple FumeFX smoke plume scene.
Usually beauty pass is maked in rendering software, but why not speed entire shading workflow by moving it to compositing process? It’s pretty much typical standart in many studios nowadays, let’s take a look how to make that.
Here is the same fluid grid with different lights by areas. Every color represent another fill angle. In our situation green color is key light, red – fill light, blue – back light.
What is cool, that in compositing every color can be separated as another pass. Three passes from just one rendering.