In case anybody wants to play with that little demo material node setup, here's is how I made it using a matmatic script.

s = Surface(RED,.5, 1, 1, .1)

white = SimpleColor(WHITE).labelled("White (255)")
two = Add(2).labelled("The number 2")
wo2 = (white / two).labelled("White / 2")

gray7 = SimpleColor(IColor(127, 127, 127)).labelled("GRAY 127")
gray8 = SimpleColor(IColor(128, 128, 128)).labelled("GRAY 128")

gray = Blend(gray7, gray8, .5).labelled("Blender:GRAY 127.5")

tile = Tile(wo2, 1, gray, 1, Mortar_Thickness=0)

s.Bump = 10*tile
 

---

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)