Renderman has been used by pretty much every VFX studio for the last 30 years [1]. I remember downloading and dabbling with it along with BMRT [2] in the early 2000s. It was the first widely used tool to have a procedural first approach to rendering.

[1] https://renderman.pixar.com/movies

[2] https://en.wikipedia.org/wiki/Blue_Moon_Rendering_Tools