If you tried to do it directly, you'd a) find it very hard as it's largely undocumented, and b) it'd probably break when the vendors decide to change it without

If you tried to do it directly, you'd a) find it very hard as it's largely undocumented, and b) it'd probably break when the vendors decide to change it without warning on their new GPUs. As for applications, well I dunno. One particular example would be Render To Vertex Buffer, something that ATI cards used to expose an extension for but NVidia cards didn't. Even though basically _any_ GPU could do it if the driver decided to. A better use would be to allow the GPU to read the game's scene structure directly without even needing an API in-between.