Also this, from the guy who ported Valves Source engine to OpenGL: http://richg42.blogspot.co.uk/2014/05/the-truth-on-opengl-driver-quality.html http://richg42.

Also this, from the guy who ported Valves Source engine to OpenGL: http://richg42.blogspot.co.uk/2014/05/the-truth-on-opengl-driver-quality.html http://richg42.blogspot.co.uk/2014/05/the-truth-on-opengl-dr... The vendors are Nvidia, AMD, Intel/Linux and Intel/Windows respectively. Yes, Intel maintains two completely separate OpenGL implementations.