I did that material by using the world position of the near clip plane. Since doing screenpos-> transform caused a crash I had to create a custom node to do it. I have an image from my twitter feed where somebody asked this same question:
Note that the 10 is hardcoded to match the default near clip plane. In VR editor the near clip plane changes based on world to meters scale. There is a way to access the frame’s actual near clip if you need that but I will have to search for it later.
No atmospheric fog. Just manual shader fog using scene depth.