I found this handy breakdown of what the different artist do for Visual effects.
Previsualization In a nutshell, you can think of “previs” as 3D animatics, or a 3D animated version of the storyboards. Although you’ll need experience in 3D software, you’ll really need to be able to deliver the director’s vision for the film into your sequences. To do this, you’ll essentially need to be a generalist that can do everything from modeling to rendering, along with video editing and some compositing skills in After Effects. Instead of trying to get everything polished, though, you’ll be foc
Source: VFX jobs and what they do