I'm running a Ubuntu machine as a client, but I need to start a 3D game to get automated screenshots, but within xvfb so it does not interfere with normal computer function. However, the game is quite graphics-intensive, so within the XVFB graphical sandbox, it fails to use the GPU. When I run it on the default X server without XVFB, it manages to use the graphics card, but interferes with use of the machine since it is, of course, onscreen. I checked out VirtualGL, but it mentions simply headless X servers, not XVFB or even ATI cards.
I have an ATI graphics card, and plan to use import to grab screenshots from the XVFB program.
So, how can I force XVFB to use a physical graphics card supporting OpenGL to run a program, in a way where I can use import to grab screenshots?