It's basically just a single texture projection that's applied as the transparency for all of the shders. I used a ramp texture but with no ramp, just a solid color. Then I turned off the wrapU & wrapV so that it would only blast what's inside the projection node and would not tile. When I set the ramp to white, everything inside the bounderies of the projection is transparant, and because I set the default color to black, everything else is opaque.

I hope that's a bit clearer. The best way to understand is to open up the hypershader, pick a material and graph it. Let your mouse wander over the connector lines and see how the different nodes connect to one another.