[userbinator]

Inigo Quilez created that site, he could be said to have been the one who really popularised it all. He has a bunch of articles on his site about distance fields:

https://www.iquilezles.org/www/articles/distfunctions/distfu...

https://iquilezles.org/www/articles/raymarchingdf/raymarchin...

He also has videos on YouTube, some of which show the creation of a scene starting from the basics.