Quartz Compositor is the windowing system that is responsible for the user interface in Mac OS X. Starting with Mac OS X 10.2, Quartz Compositor was extended by Quartz Extreme, which uses OpenGL to render screen displays faster by presenting them as textures within a 3D OpenGL context. This permits faster compositing of screen images using 3D hardware acceleration.
To use Quartz Extreme, the Macintosh must have an AGP graphics card with support for arbitrary texture dimensions and a minimum of 16 MB of VRAM. In practice, this means either any nVidia or an ATI Radeon or better.