How do you calculate the sky view factor (SVF) from Google Street View images?

[Kauan Mateus Kubaski]

I would like some code or some way to get stereographic images (like fisheye lens ones), something like this does: http://notlion.github.io/streetview-stereographic/#o=1,0,0,0&z =1.64&mz=19&p=-25.09635, -50.15856&fw=1 but preferably just the circumference. There are also problems that if I printscreen, there are differences in the SVF calculation according to the screen resolution, which makes it difficult to repeat the methodology (a flaw for its scientific use), or how to be applied by some WebGL or JavaScript tool. From what I've seen, a RayCasting is used, a form of 3D rendering.

Also, I saw that Hugin himself does this conversion for stereographic projection but how?