David Pogue does a nice job examining the question
… where would you draw the line and say “That’s not photography anymore?”
I think you will find the answer isn’t as obvious as you might think. Bottom line is that I think David is correct in his view that where the line is depends on the application and context. E.g., compositing is OK for advertising, but definitely not OK for new photography. A photography competition is another set of values — where I would say absolutely no compositing, unless it is a special category for such digital products.
I think you will find the way David lays out a progression from “raw image” to “3D modeling” a useful prod to your own thinking.