Years ago in college I did a bit of work on a nuclear physics simulator (think: reactor modeling) that based its geometrical model on implicit surfaces, specifically R-functions (of which min(x,y) is an example), which have some neat properties such as being differentiable everywhere. This is a good introduction (and probably the only one in English): https://ecommons.cornell.edu/items/35ae0f68-1af5-4f28-8b8b-7...

I've been away from the nuclear field for a while, but I imagine it's still using a lot of legacy Fortran codes to do modeling. Fidget has some interesting possibilities as a kernel for a new simulation package.