Ah I see, so they compute a lookup table first then go from there. I could probably make that LUT a static texture somewhere as well. I’ll have a second look.
The difficulty is figuring out how to do multiple samples in the Material Editor, since I can either have a huge duplication of nodes, or I have to use HLSL. Unfortunately the HLSL versions all seem to require calls to other functions, which prevents me from using it at all. Also means it won’t cross-compile to Android either.