Why are some material nodes connected to themselves? Here's a small thing I've been wondering about for a while: Occasionally, when I import models from other sources (e.g. 3ds Max -> FBX -> Blender), I see in the Node Editor some nodes which are apparently connected to themselves. Like so:



Can somebody explain what's up with that? How is this self-connection useful? How can I do it in Blender?
The node is not connected to itself, it is muted. You do that to a node by pressing M. The red line indicates a "pass-through" - the input goes straight to output and the node is disabled.

I would guess the script that creates the node network always makes the full tree and just mutes the nodes that are not used in the original material, like normal mapping in this case.