How can I make an island plane? I believe I have the right term, but just to be clear, I want a plane that is entirely bounded by another plane on the same layer, with a small separation between them. I'm using positive planes. I've experimented with using geometries on the Anti-Etch layer and with the Edit->Split Planes->Create command, but nothing has worked so far. Thanks so much!!
Update: I realized that I can make exactly the shape I want by just placing a filled rectangle on the etch layer, then placing a rectangular void inside of that. However, if I make my own "power plane" in this way, placing through-hole parts through the plane causes DRC errors ("thru pin to shape spacing"). The void doesn't seem to do anything when I place it on the auto-generated power plane shape. Can someone please help me understand this? Is the Allegro tool designed specifically to prevent the creation of island planes like this?