Creating Complex Natural Materials in Cycles - Blender 2.6 Cycles: Materials and Textures - page 170

9. First, we expose the colors: click on the Color input socket of the first
Diffuse shader inside the Color frame and drag it to the extreme left to
the border of the group interface. Rename the newly created input socket
as Diff_Color1 . Do the same with the second Diffuse shader and re-
name the new socket as Diff_Color2 . Repeat this for the Color socket
of the Glossy shader and rename the input as Spec_Color .
10. Now click on the Fac socket of the second Mix Shader node inside the
Color frame and drag it to the left as well; rename it as Spec_Amount .
11. Expose, too, the Roughness socket of the Glossy shader.
Now we have to find a way to expose a single input value to drive the scale of all the
texture nodes and also need one single input value to drive the three Bump nodes
piped to the Normal sockets of the three shaders, keeping at the same time their
individual starting values.
1. Add a Math node (press Shift + A and go to Convertor | Math ) and move
it closer to the first Voronoi texture inside the 2nd Bump frame. Set the
operation to Multiply and, in the first Value slot, copy the Scale value of
the Voronoi texture. Connect the Value output to the texture's Scale in-
put. Set the second Value to 1.000 and drag it to the left; rename the
new interface input as Scale .
2. Press Shift + D to duplicate the Math node, move it close to the following
Musgrave texture node, copy the Scale value, and drag the second
Value input to connect it to the Scale new input on the interface. Connect
the output of the duplicated Math node to the Musgrave scale input.
3. Repeat the same process for all the textures inside the 1st Bump and
2nd Bump frames, at the end you should have added and connected
eight Math nodes.
4. By clicking on the little upper arrow on the side of the Scale interface in-
put, move it before the Spec_Amount node.