Exactly as for Blender Internal, Cycles materials can be linked from libraries. Every blend file containing linkable assets can be a library.
Linking materials is really a useful practice: let's say you have 20 different blend files with objects using an iron shader, and that at a certain point of your workflow you need to modify this iron material in all the files; by having this material linked in all the 20 files from a single blend is possible to update all of them at once by modifying just one shader in one file.
- Just go to the File menu in the left part of the main header and select Link:
- Browse to the directory where you store your library files and select the blend file you want to link the material from (for example, try the file
1301OS_02_library.blend). - Browse inside the blend structure, where the linkable assets are divided into subdirectories (shown as folders named as
Scene,Mesh,Material,NodeTree,Object, and so on; note that the various folders appear only if inside the blend file the corresponding asset to be linked actually exists). - Click on the
Materialsubdirectory. Once inside, select the material you want to link (for example,Material_04) and press Enter to confirm (or click on the Link/Append from Library button on the top right). - Now click on the Material data block button on the header of the Node Editor window and select the name of the linked material, the one labeled with a LF prefix, L is for Linked and F is for Fake User.
- This because, in the library file, we assigned the Fake User to the material by clicking on the F icon on the side of the Material name data block. If not assigned to any Fake User, the prefix of the linked material would have been L0, that is Linked and 0 Fake Users inside this blend file (for example,
Material_05, which is simply assigned to the object but has no Fake User). - The name of the material is grayed out to show that is a linked one; on the side of the name a new icon has appeared, a little arrow, and the users number has been updated to 2 (the Fake User and the object we assigned the linked material to).
From now on, every modification we make to the material in the library will be reflected in the linked material at the moment we load the file.
Not only can materials be linked, but also node groups: in this case, instead of the Material subdirectory to link from, choose the NodeTree subdirectory, and then select one or more node groups you want to link.
The data block name of a linked node group is grayed as well; you can modify the exposed values and colors but if you try to enter edit mode a pop up asks if you want to make the group local; if you confirm, the node group becomes editable but, of course, local and no longer linked from the library file.