I’ve been doing the same for a couple months for a university course. If you haven’t figured it out yet, my advice would be review OpenGL 3D code and then look through the example programs that come with your Vrui Toolkit. I’ve managed to get a sphere bouncing around the screen though am having some trouble with Vrui’s navigation settings. Bottom line is it’s doable. Also if it wasn’t immediately obvious, the language is c++.