Do you think 3ds max and similar programs use DirectX or OpenGL?

Question

API

In fact, all their work is based on using some kind of graphics API, right? Indeed, without this API, they would not be able to write a program for working with 3d graphics. Or am I wrong and there are other ways to write graphics programs without using these standard APIs? But then the process becomes more difficult.

Answer 1

You can do everything by hand, without using the API, but why? (here is a small course on how to do it https://habrahabr.ru/post/248153/)
3d max uses API, there even in the settings at one time there was a choice between OpenGL and DirectX.