You use clusters to render a whole/movie scene when it's finished or in various stages of completion to show to the art directors but you still need powerful wo

You use clusters to render a whole/movie scene when it's finished or in various stages of completion to show to the art directors but you still need powerful workstations to preview your own changes to the scene as you work on it. Plus, clusters aren't always at your disposal and usually have schedules when you can book them according to priority and not all workflow can be automated and pipelined to fit a cluster. VFX work is not just 3D modelling where you click Render and boom, 2 days later, your scene it's ready to be put on film. There's tons of tasks you need to do pre- and post- production like layout, rigging, motion capture, rotoscoping, comping, etc. and most of these tasks are done manually on the artist's workstation. I'm sure big houses like ILM, Pixar, Weta, Disney have the money and technical chops to engineer and maintain their own in-house rendering cluster infrastructure but small firms don't and rely on beefy workstations like this to render their project over multiple days.