http://developer.download.nvidia.com/opengl/specs/GL_NV_copy_image.txt
http://www.opengl.org/registry/specs/AMD/wgl_gpu_association.tx
http://developer.download.nvidia.com/opengl/specs/GL_NV_copy_image.txt
http://www.opengl.org/registry/specs/AMD/wgl_gpu_association.tx