Spherical Harmonics for PyTorch - and pure PyTorch ngp

[cheind]

Hey,

I've stumbled upon your idea of using sympy to generate CUDA code to compute spherical harmonics and its derivatives, which I found a really nice approach!

In case someone is interested, I've reworked that approach in a more generalized manner to generating auto-diffable spherical harmonics for PyTorch here

https://github.com/cheind/torch-spherical-harmonics/

I'm using them in my (work-in-progress) pure PyTorch version of ngp

https://github.com/cheind/pure-torch-ngp