The devil is really in the details. Pixar and Disney throw scenes at Renderman for overnight rendering jobs where each node loads up to terabytes of data per frame (geometry, textures, volumes...). So the renderer contains tons of tricky optimizations under the hood to support that crazy amount of data. Other renderers like Cycles use pretty much comparable physical models for everything and create almost identical output for simple scenes. But most of them would crash and burn spectacularly of they had to deal with scenes at the size these studios produce.

[Even though you could theoretically generate a lot of detail, especially textures, algorithmically on the fly, nobody goes for that: the only known good way to band limit textures for level of detail reduction without aliasing artifacts is to sample and filter them - generating the whole texture anyway.]

In the industry, studios will have different tech stacks that make them competitive for different areas. Some will have specialized simulations software for fluid dynamics, others really advanced rigging techniques that allow super realistic results faster than competing studios. A lot of it comes down to custom pipelines and integrations depending on their needs.

The off-the-shelf tools have come a long way for a lot of tasks, but studios still create really awesome in house software that in a bidding situation (VFX) can help a bit. Though to be frank the bidding process is an absolute mess.

When it comes to rendering, it all depends on the focus of the projects and the direction/needs of the studios. Though the end results may be similar, the way you get there will have varying degrees of optimization and flexibility depending what the stack is built on (besides the typical necessities of traced rendering).

Some examples:

- Pixar: Renderman

- Weta Digital: Manuka [0]

- Framestore: Freak [1]

[0] https://www.wetafx.co.nz/research-and-tech/technology/manuka...

[1] https://web.archive.org/web/20210126083056/https://beforesan...