There is only one vertex buffer per patch that contains all of the vertices. Index buffers are being used, all of them pre-generated of course and uploaded to t

There is only one vertex buffer per patch that contains all of the vertices. Index buffers are being used, all of them pre-generated of course and uploaded to the graphics card. Rendering a patch then becomes a simple matter of selecting the right index buffer (or index buffers, since stitching requires more than one drawing call).