axalon

if it's the writer pitching, it probably helps zero. the director works with the vfx supervisor or works with the art department to do that sort of thing. if it's you wanting to direct your own material you need that at some point, but a resume is what studios are looking for. then you get into budgeting and then visualization!

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It also depends on the project. I'm a comedy writer and have never felt the need to bring in concept art. But if I were pitching a sci fi project, I'd definitely consider it.