First, good effort by Carolina (except for their last kickoff). Their offense (at least, from the point in which I joined in the second quarter) remained cool. So close....
In any case: if, like me and some friends, you've been fascinated by the "first down stripe," I've found a Wired News article about it from 1999. I don't know if it's changed much since then. It fits one of the theories I've had in my head for a while, which is that a 3D representation of the stadium must come into play so that the line moves with the cameras by knowing where the current camera in use is and which way it's pointing.