title: How much of a modern graphics pipeline uses dedicated hardware?
body: <p>To put the question another way, if one were to try and reimplement OpenGL or DirectX (or an analogue) using GPGPU (CUDA, OpenCL), where and why would it be slower that the stock implementations on NVIDIA and AMD cards?</p>
  
  <p>I can see how vertex/fragment/geometry/tesselation shaders could be made nice and fast using GPGPU, but what about things like generating the list of fragments to be rendered, clipping, texture sampling and so on? </p>
  
  <p>I'm asking purely for academic interest.</p>