Mixed-reality recording, i.e., capturing a user inside of and interacting with a virtual 3D environment by embedding their real body into that virtual environment, has finally become the accepted method of demonstrating virtual reality applications through standard 2D video footage (see Figure 1 for a mixed-reality recording made in VR’s stone age). The fundamental method behind this recording technique is to create a virtual camera whose intrinsic parameters (focal length, lens distortion, …) and extrinsic parameters (position and orientation in space) exactly match those of the real camera used to film the user; to capture a virtual video stream from that virtual camera; and then to composite the virtual and real streams into a final video.
Figure 1: Ancient mixed-reality recording from inside a CAVE, captured directly on a standard video camera without any post-processing.
