This is something that I was searching for before and found when I wasn’t looking for it (why does that always seem to be a trend). This is an example program that will render a png (a simple triangle) using OpenGL and EGL on the command line without needing X11. Though now that I found it I can’t remember what it was that I wanted to render with OpenGL on the command line. Either way, great find.

https://github.com/matusnovak/rpi-opengl-without-x