Pixar's Render Farm

If there's a generally static scene with just characters walking through it, does the render take advantage of rendering the static parts for the whole scene once, and then overlay and recompute the small differences caused by the moving things in each individual sub frame?

Or, alternatively what "class" of optimizations does something like that fall into?

Is rendering of video games more similar to rendering for movies, or for VFX?

What are some of physics "cheats" that look good enough but massively reduce compute intensity?

What are some interesting scaling laws about compute intensity / time versus parameters that the film director may have to choose between? "Director X, you can have <x> but that means to fit in the budget, we can't do <y>"

Can anyone point to a nice introduction to some of the basic compute-relevant techniques that rendering uses? Thanks!

As for your questions:

> Is rendering of video games more similar to rendering for movies, or VFX?

This question is possibly based on an incorrect assumption that feature (animated) films are rendered differently than VFX. They're identical in terms of most tech stacks including rendering and the process is largely similar overall.

Games aren't really similar to either since they're raster based rather than pathtraced. The new RTX setups are bringing those worlds closer. However older rendering setups like REYES that Pixar used up until Finding Dory, are more similar to games raster pipelines. though that's trivializing the differences.

A good intro to rendering is reading Raytracing in a Weekend (https://raytracing.github.io/books/RayTracingInOneWeekend.ht...), and Matt Pharr's PBRT book (http://www.pbr-book.org/)