Vilters that's nonsense. We're discussing combining displacements. These are not colors. The amount of displacement could be .0005 inches or 5000 inches. The numbers we type into the Displacement parameter are the same numbers we type into a Math:Add node, and then those numbers get multiplied with the next number you plug them into and so on.

Even if we were dealing with colors, there most certainly are colors (vectors) in the material room math that are whiter than white and blacker than black. I've discussed these dozens of times.

The color math is just three copies of ordinary math. It's not different math.

You are confusing what you can DISPLAY with what numbers are possible. You can only display 0 to 255 but all other numbers are possible.

There are no limitations in the Math:Add node. It can do everything a Blender does and more. It is the Blender that is limited. It can only mix two inputs so that the total is always a constant.

The Blender node is built (internally) upon Math nodes as follows:

 

Blender(v1, v2, f) = Clamp(1-f)*v1 + Clamp(f)*v2

See the + in the middle? That's a Math:Add node. A Blender is a kind of limited-function adder.

See how the v1 and v2 are multiplied with opposite values (1-f vs f)?

That means as the blending factor of one goes up, the other must go down.

With the Math:Add node the user can just change either number without affecting the other. That is more useful in the case of combining displacements.

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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)