Managing Cycles Materials - Blender 2.6 Cycles: Materials and Textures - page 65

only if inside the blend file the corresponding asset to be linked actually
exists).
4. Click on the Material subdirectory. 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).
5. 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.
6. This because, in the library file, we assigned the Fake User to the mater-
ial 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).
7. 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 reflec-
ted 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.