Its been years that I wanted do this sort of shader. Was constrained by time, work and lack of math skills. Quarantine sort of changed all that. So I got around to doing it. Using resources from GPU Gems 2, Alan Zucconi's tutorial on the subject. I was able to make an implementaion, understand it and tweak it to produce a result that satisfied my aesthetic.

Click to see the video of a day cycle using the shader:

There is more to be done in this project and I will eventually get to it. But for now there are more shaders to be made and more knowledge to be gained.