I often need to layout with negative film approach. It's like the Spliting Plane, but I only draw lines for which I want to clear. It's easiler. But this method cannot check open or short circuit. Does anyone know which software support this work. Or how do you do it?
Is there a particular reason why you have to use negative planes?
For the very reason of verification many designers are moving away from using negative planes. Myself included.
But I do know from experience that the way Protel creates negative split planes is verifyable. Connectivity, thermals, etc..
As of late I no longer use Protel. But its a pretty good bang for the buck.