This morning the HTC Vive officially went on sale, and with it, a launch of Valve's Steam VR initiative. To bring on a greater understanding of what this new environment is like, Valve set out to create a single video which showed what virtual reality was like for the user. To do this, they needed a bit of Mixed Reality. That is a green screen room, a 3rd-party camera, and an HTC Vive. To do this, they needed to be able to track outside the user - to do this, they needed to attach a Vive controller to their camera rig.