As far as we know, the only obj to vtx conversion that makes sense is the process of turning 3D OBJ files (.obj) into anim8or 3D models (.vtx), which can only be done with the software itself.
Anim8or is a popular 3D modeling and character animation program and supports OBJ format by default, so it's actually one of the main ways how to add and reuse existing 3D content in the software.
You can find dedicated tutorials about Anim8or on the Internet and tutorial ebook by Ian Ross was released in 2021 as well.
Updated: January 3, 2024