Materials and Shader Trees
In the SLA shader there is a 3D wood shader, but it is volumetric and therefore quite difficult to handle if you're attempting individual additions such as roughness or color variations. The Channel shader is faster and more flexible here, as it behaves like normal image data in standard C4D materials.
The Power Gradient
The Power Gradient is a sample shader that is supposed to demonstrate for programmers how to work with C++ commands toward individual shader development. It is not contained in normal releases of C4D, but you can download it separately and for free from the Developers' Corner of Maxon's Web site. There you'll also find documentation for all C.O.F.F.E.E. commands including short examples and comments. ...