What’s the best way to create like a layer mask so as the hand moves up I can slowly reveal a portal opening from the bottom of the door to the top of the door as the hand moves?
a holdout mask with transaprency
So I add an object in front of the door with the holdout shader and have the object expand upwards? Is there a way to make the object with the holdout shader only make specific objects behind it transparent?
No, there is no way to do that.