The only time I had access to Renderman documentation was during my thesis, porting a particle based visualization engine from Objective-C/NeXT Cube into a plain Windows/OpenGL 1.1/MFC.

Reading that, alongside "The Renderman Companion: A Programmer's Guide to Realistic Computer Graphics" was eye opening how far behind regular PCs were from such graphical workstations.

Naturally that was about 20 something years ago, very interessing to see how much Renderman has moved beyond that, and the evolution of programmable GPGPU as well.

https://www.amazon.com/-/en/Steve-Upstill/dp/0201508680

OpenGL would have been better if that role had been taken by Iris Inventor.[0]

Instead it became a rite of passage for every OpenGL beginner to reimplement Inventor on their own way, either from scratch or playing Tetris with different kinds of libraries.

Meanwhile, other graphical SDKs always provided such APIs.

By the way, the best 3D API back then was Renderman, the genesis for modern shading languages.

https://www.amazon.com/RenderMan-Companion-Programmers-Reali...

[0] Yes there was Open Inventor afterwards, but its story is a bit convoluted.