matmatic is a Python script I wrote for Poser. You can enter expressions for shaders in matmatic scripts, using the full power of the Python programming language plus the matmatic library, and it produces ordinary Poser nodes that implement what you said.

For example - this is a matmatic script for a typical GC shader that anti-gamma corrects a color map image, produces balanced diffuse and specular effects, and then gamma corrects the output.

s = EmptySurface()
gamma = PM(2.2, "Gamma")
map = ImageMap().labelled("Color Map")
spec = Blinn(WHITE, .1, .4, 1)
EmptySurface(Alternate_Diffuse = (Diffuse(map ** gamma, .8 * (1 - spec)) + spec) ** (1 / gamma))

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)