   VFACE semantic and normal vector
  Hi,I'm working on my deferred renderer. Now I need an extra channel to store a data in my G-Buffer. But my G-Buffer is full.Now I'm thinking that I can store Normal.xy then reconstruct Normal.z by using Normal.z = 1 - dot (Normal.xy, Normal.xy) equation.I don't know whether Normal.z will be calculated correctly or not. I mean, you know, sign of Normal.z value is important (at least for me).Now, this is the question: can I use the VFACE semantic (a floating point value that indicates a back-facing primitive) to determine the sign of Normal.z value? Like this://suppose PS_In.vface is a VFACE value used in pixel-shaderNormal.z = sign(PS_In.vface) * (1 - dot(Normal.xy, Normal.xy));Thanks in advance.Rohat.   
  Yes, i think you can.VFACE is a floating-point scalar that indicates a back-facing primitive. A negative value faces backwards, while a positive value faces the camera.So you can use that equation in order to detect Z sign.   