Author here, yes you are correct that it's Simplex noise. I also use a method of domain warping, I used this article as reference https://iquilezles.org/article

Author here, yes you are correct that it's Simplex noise. I also use a method of domain warping, I used this article as reference https://iquilezles.org/articles/warp/ https://iquilezles.org/articles/warp/