Now the middle sheet has no displacement. It appears in its natural position. Being .001 inch above the green sheet, it's blocking our view of the green sheet.

The surface color of the middle sheet is receiving 3-tuples from the Clouds node. Since Diffuse_Color expects colors and we're sending colors from the Clouds node, no conversion of the input is happening. The color of the Clouds node is multiplied with the white color chip of the Diffuse_Color input, which actually does nothing to it. Then it is multiplied with the Diffuse_Value. That's a number. The number is first converted to a color 1, 1, 1 - if you're tracking well, at this point you recognize that is the tuple represention of the color white. Then that color (white) is multiplied with the cloud color - again doing nothing at all to it. (1 * x = x, 1 * 1 * x = x, 1 * 1 * 1 * x = x)

Then the internal Diffuse node does its work reacting to my light (which is an infinite) and computes a color which appears in our render. Since the infinite light is at a high angle of incidence, and its color is also 1, 1, 1, the resulting rendered sheet looks a lot like the Clouds node itself.

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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)