Certain items in the main material node have have a color and a value, e.g, Diffuse_Color and Diffuse_Value. Normally the Diffuse_Value is simply a number that sets the intensity of Diffuse_Color, but sometimes I see other nodes connected to the Diffuse_Value as well. What's going on with that?

Ok, Node gurus (bagginsbill?) care to show us the skinny?

Not a guru by any means but in simple terms, you can use another parameter, or set of parameters to control the Diffuse Value, should you wish.

Example: You have a piece of chest armour which is, say, red and you want there to be a bit in the middle to glow blue. Create a texture map of the bit you want to glow, with the red part in white and the glowing part in black. Connect this to Diffuse_Value. You'll see there's now a black area on the armour, right?

Select the Ambient Channel, set that to Blue and Ambient_Value to 1, or any other value, depending on the brightness you want. Connect an inverse version of your texture map to this, either using a math node to invert it, or by creating one in Photoshop.

You now have a red bit and a blue glowing bit with no conflict between either.

There are limitless uses, depending on your needs. BB is quite possibly the absolute all time expert in using any and all of the nodes to best advantage, so no doubt he can give you many more ideas.

Sam ... you have always been a guru in my book, thank you for posting!

Thanks for the kind words but I'm more of a "I wonder what that does... Ooops!" sort of guy.

Anyhow, It just occurred to me of another use, one which I do quite a lot on my Dalek models. On the "Classic" Daleks, they have a mesh collar wrappped around the midsection (known to us Dalek geeks as shoulders). The shoulder mesh on my models is a transmapped sort of cylinder which uses a mesh pattern and displacement to make it look like the real deal. The transmap plugs into Transparency, Diffuse_Value and Specular_Value, which kills off any colour and specularity where the holes are supposed to be, thereby reinforcing the mesh like appearance. I add a small amount of displacement to give it some thickness et voila!

That is fantastic! What a great tip!! I will definitely keep this in mind.

Sam, could you share the settings on the collapsed nodes? clouds, u and v texture coordinates?

Boni, the U & V coordinate nodes are read-only; they have no inputs to show, and the little preview window will only show a linear gradient (left-right for U, up-down for V). They output the UV map coordinates. By connecting them into the Tile node's U & V offsets, you can rotate the tiling so that it runs diagonally. (You could also flip/mirror). The Cloud node has inputs and numeric adjustments, and its mini preview window is useful. Looks like Sam is giving the metal some surface variation with the Cloud->Blender chain.

Having just a numeric value in a "value" socket applies a constant value all over the material zone.

You can have that value vary by mapping the changes (use an image map or movie node as a mask, or use one of the texture nodes such as Tile).

You can apply a 3D texture node which will apply to the geometry even without UV mapping (Cloud, Spots, Cellular, Turbulence, Noise, etc.)

You can vary the value by math/geometry variables (frame number, N, P, u, v, dPdu & dpdv, etc.) - These can do things like react to edges/corners (wear scuffing on a metal crate), or apply only to topside horizontal surfaces (snow on rooftop)

Oh, thank you ... more wonderful things to learn about the material room and nodes.

As Seach stated, there's nothing useful to see with the U and V; the Clouds node is simply a black and white cloudscape to give the metal a bit of variation. You can easily play around with the values in there to get something you like. I wanted to give an impression of an unpainted metal casing, rather than a specific colour. You can see the effect on the render, where the vertical slats sit over the mesh.

I attached it through a Blender just in case I wanted to add something else, such as scratches or dirt, or whatever.

This is great knowledge. Very helpful as I suffer with my own transparency and material issues. I want to figure it out the Sam Therapy way but after a couple of weeks of fighting it, a little push and a little hint from Sam and seachnasaigh is a very good thing.

Good question, Good answers.