This is the Invisible House, which I saw when I went to the future. It was being used to protect our leaders and important buildings from attackers and terrorists. The outside is constructed out of LCD panels and has four cameras, one on each side. Each one projects what it sees on the opposite side, so you get the illusion that you are gazing through it. For the problem of windows, there are TVs on the inside that reveal what the cameras see, so it seems that you are looking through a window. To protect a flat roof there is a camera that watches a patch of grass or whatever material that surrounds the building, inside the building and it projects that onto the roof.