http://renderingpipeline.com/2014/06/whats-the-big-deal-with-apples-metal-api/ http://renderingpipeline.com/2014/06/whats-the-big-deal-with... That blog post s

http://renderingpipeline.com/2014/06/whats-the-big-deal-with-apples-metal-api/ http://renderingpipeline.com/2014/06/whats-the-big-deal-with... That blog post should help you clarify the difference. I think the primary problem it that OpenGL and DirectX handle changes in pipeline state very poorly.