Gradient
The C4D Gradient node is for using the Cinema 4D's "Gradient" shader. It should not be confused with the Octane Gradient node, because each has differing functions. The Octane's Gradient Texture node is described here. You can read what the C4D Gradient Shader is and what it does in the Cinema 4D help file, or you can go to this link for further information.
How to Use
Open the Node Editor and prepare the setup as you see in the image below. Here, the C4D gradient connected Diffuse channel of the material. You can use this gradient with all Octane Nodes that have "power" and "texture" inputs. This node must be rasterized (baked) for every frame and higher resolution will consume more resources.