Documentation of rather complex functions do not exist

[Slamy]

First of all. I love this project. You seem to put a lot of effort into this.
But to make it usable for other people, there is more documentation required.
Especially with functions like CompMatrixLV and ApplyMatrixLV. There is no documentation at all about these and I have a hard time.
I would encourage to use something like Doxygen to describe the functionality and replace the manually written documentation with a automatic generated one.
The nice thing about Doxygen is that some IDEs are even capable of presenting these descriptions as you write your code.

If you are not entirely sure about how to start with a Doxygen project I would offer to kickstart it for you with a pull request and some examples with the functions I do understand.

[Lameguy64]

GTE documentation is still a work in progress at the moment. Suppose I'll prioritize documenting the more advanced matrix functions over GTE opcode macros which are already documented in numerous other places.

[Lameguy64]

Most of the GTE functions including CompMatrixLV and ApplyMatrixLV are now documented in the library reference. GTE opcode macros are still a work in progress, but the GTE documents in nocash's PlayStation specs document which you can find in https://problemkaputt.de/psx-spx.htm#geometrytransformationenginegte may suffice. GTE command names are prefixed with gte_ when using C in-line macros.

[Slamy]

Thank you Sir for your fast response.
Also yes, this problemkaputt page is very helpful as it shows the inner doings on the lowest level.
I still do believe that doxygen would be a better approach as it means less work for the person which writes the documentation.
But this is your project so you should decide what's best.