I am trying to apply a rectangular (closed-path) alpha mask or window in After Effects to block out a rectangle shape on one layer, and then apply an inverse of same mask to layer beneath it to let layer beneath it show through window. The masks aren't working. When I set mask mode to "add" or any other setting, the masks block both layers completely. I have applied CC Cylinder effect to both layers to wrap images around a cylinder. Do I need to do something first to the layers, like precomp them, before I apply mask to each layer?
Provide screenshots of the comp and timeline.