An augmented reality interior designing app

I want you to create an augmented reality interior designing app. I should be able to change the wall colors and floor(& roof) color/design of the room that I see through my phone camera. It is not the matter of replacing the color code. You have to properly identify walls, roof and floor. However I feel some of the practical issues should be addressed before implementing this app. So please include detailed technical solutions that you are going to apply to following issues in your Proposal. If I am impressed with your proposal we can proceed to implementation. 1. In augmented reality we track a point and place a 3D model relative to that point. But that is not the case in this project. You can't track a particular point. So explain me how are you going to identify walls, floor, and roofs and track them? 2. How are you going to identify x,y,z axis to get the 3D view(I am not sure whether this is required to implement this app) 3. How are you going to identify different sides of walls when the color is same? 4. When changing the color or design how are you going to maintain the 3D effect? 5. When there are furniture covering the walls how are you going to handle that scenario?