I am trying to write a shader to read the whole frame, pixel by pixel and after some calculations re-write the pixels. I have looked through some codes but most of them were not relevant. Could you give me some hints on how I can read pixels and write pixels in Unity shader programming?
If you have the Pro version of Unity, you can achieve this with image (postprocessing) effects. All you have to do is to implement the OnRenderImage callback on a component of a camera. Then you call Graphics.Blit with a material which has a shader. The shader receives the screen contents as main texture.