   ZBuffer
  How can I get a pointer to the ZBuffer so that I can do screen space calculations?   
  Which D3D version are you using?   ;  DX9   ;IDirect3DDevice9::GetDepthStencilSurface;  I'm pretty sure you don't want to go anywhere near the Z-buffer. You can get a pointer to it, but you can't access any of the depth values unless you use a lockable format (which not all cards support). What sort of "screen space calculations" are you trying to do?   