When CGI is overlaid onto an existing piece of video, and the spatial geometry of the CGI matches that of the video - it's most noticeable when it's hand held. What software is used to determine where the video camera is in the 3D world? Never mind the actual generation of the CGI or the compositing, just how does one work CGI into the 3D world of the video? I can't believe it's done by eye frame by frame...