With 10-grit, for instance, sometimes the collapsed spectral range is quite noticeable, while other times the range could be larger. By varying the curve, you'd further optimize visual quality and compressibility. Finally, it might be worth looking at the 216 values that are exactly in-between adjacent cube values. So long as you permit enough off-cube intermediates to avoid the chunky cartoon look, you come out ahead. If you'd like to improve, extend, or prepare other realizations of this stuff, and make your work publicly available, please contact the author Todd Fahrner at Verso.
Verso places the scripts and underlying algorithms into the public domain.