This replaces the opengl dynamic library, similar to apitrace. It should work for any opengl app (the example they use is a simple gl app that draws some spheres). When the app makes an opengl call, it logs it to tmp before forwarding it on to the real opengl library. It's kind of like strace for graphics...

Then, there are tools to analyze and inspect those logs. You can presumably replay a frame, and step through each GL call and inspect the data it is sending. I haven't tried building this yet, but it looks like it includes a tool to replay the GL calls, and some kind of interactive GUI.