The problem with OpenGL was that it was never officially supported or evangelized by Microsoft. Of course, Microsoft has always advocated its own Direct3D driver model over OpenGL, but GPU manufacturers have long supported OpenGL in drivers. Many games and productivity applications still use OpenGL even today. With Windows Vista, Microsoft made it clear that OpenGL support would only work as a layer sitting on top of Direct3D. There was going to be translation involved and thus, a performance hit.
This week the Khronos group, which is responsible for developing and maintaining OpenGL, has released a report indicating that OpenGL support will now be natively supported in Vista without layering over Direct3D. Using standard Windows installable client driver (ICD), OpenGL will be fully accelerated and be fully compatible with Windows Vista's Aeroglass UI. In fact, Khronos says that by the time Windows Vista ships, Aeroglass performance on OpenGL will be superior to that of Direct3D. According to Khronos and NVIDIA:
* Hardware overlays are not supported
* Hardware OpenGL overlays are an obsolete feature on Vista
* ATI and NVIDIA strongly recommend using compositing desktop/FBOs for same functionality
However, the OpenGL ICD drivers must still be downloaded and will not ship on the Windows Vista installation disc. Khronos said that NVIDIA already has a beta 2 ICD OpenGL driver available and ATI will release its own soon. If no ICD is present, Windows Vista will rely on the layered OpenGL mode by default and only offer basic functionality.
