If I made a CGI movie of the idea and disseminated it publicly, could that count as prior art that would prevent someone else from monopolizing the idea?
Given that, anything that is published publicly, and upon which a date of publication can be proven, can serve as prior art for a patent.
But, also keep in mind that after one year, your movie would also block you yourself from patenting the material in the movie as well.
Even if your animation is admissible as prior art, there is nothing stopping someone from pattenting so much of the implementation process that you are still effectively prevented from pursuing it.