Not perfect but good enough to serve as an example now.

The bad:

• Somewhat inefficient, uploads one model matrix for each cube every frame, and even when cubes are static (should run well on pretty much all hardware, especially VR capable)
• autotools build missing
• not sure if all hotkeys still work
• math_3d.h is from an external project (MIT license), can be replaced later
• HMD origin is on the floor - HMDs without positional tracking are stuck on the floor.

Move the floor a bit down? Then HMDs with positional tracking are floating too high. Make HMDs without positional tracking report a constant y pos of about 1.8meter?

The good:

• It works
• It demonstrates how to render into a texture and then in a second pass render the texture with distortion correction to a window with gl3
• It renders blocks representing the controller position (TODO: dummy controllers always in (0,0,0))