Yesterday I asked and solved my problem:
Today I tried to change the script(from yesterday) and apply it to the camera and it did not work.
Every pixel which is printed on the Display has a depth (float), is that right?
Based on that Depth - I want every object to fade grey, relative to the screen distance to that "pixel".
Is this possible?
Or do I have to use that vertex/fragment shader on every single Object and Plane and Sky and everything in the world?