Creating Natural Materials in Cycles - Blender Cycles Materials and Textures - page 105

38. Add a Frame, parent the three nodes to it, and label it GRANULARITY, as shown in
the following screenshot:
One more bump effect frame
39. Duplicate the Add_Bump01 node, and label it Add_Bump02 , and paste it between
the Add_Bump01 node and the Material Output node. Connect the Grain_Strength
output of the GRANULARITY frame to the second Value input socket of the
Add_Bump02 node.