Check out the "SummonScript surface level details demo" demo:

https://www.youtube.com/watch?v=o58s1bPI1ZA

This is the first time I ever heard of signed distance fields, but apparently they're not a new idea. This article from Nvidia is from 2006.

https://developer.nvidia.com/gpugems/gpugems3/part-v-physics-simulation/chapter-34-signed-distance-fields-using-single-pass-gpu

This more recent article explains more of the mathematics of it.

https://jasmcole.com/2019/10/03/signed-distance-fields/

The libfive library mentioned for solid model rendering is here:

https://github.com/libfive/libfive/blob/master/README.md

The algorithm it uses to do the rendering is explained here, in this paper, "Isosurfaces over simplicial partitions of multiresolution grids":

http://faculty.cs.tamu.edu/schaefer/research/iso_simplicial.pdf

"Every six months, I have to spend a day re-deriving how Quadratic Error Functions work. This write-up is to save my future self from doing that work again. This page is based on notes that I took while working to implement 'Isosurfaces Over Simplicial Partitions of Multiresolution Grids' in libfive.

https://www.mattkeeter.com/projects/qef/