Quote - For the curious, this is the part of my matmatic script that calculates the value to plug into transparency.

cosA = EdgeBlend(1, 0, 1).asNumber() + .00001

fx = cosA ** 2
gx = 1 - (1 - fx) / (IOR ** 2)
b = opacity
a = density
factor = 1 / Sqrt((1 - b) * gx + b * fx)

y3 = 2 * a - a * a
transValue = 1 - (1 - y3 * b) ** factor

Cool.  Thanks for showing us the matmatic formulas.  I have downloaded your second material set.  Now if I could just figure out which among the 68 nodes plus belong to above matmatic formulas...