what is the viewer node, do I need it to follow along?

He has a viewer emission node connected to the light path node, i don't know what this is or why he is using it, or what it does.

  • Omar Domenech replied

    That was just an old way of visualizing what your nodes were doing, but that has been discontinued. Now it makes all of that under the hood without you noticing, so do not worry about it, we have all forgotten that by now. 

  • Adrian Bellworthy replied

    It was part of the node wrangle add-on, with the the add-on enabled the SHIFT+CTRL+CLICK added a viewer node and connected it as needed.
    Now the Material Output does it all without adding an additional node.