1st and Ten

Well not all of the Nerd Herd may have the appreciate for pro-football that I do but you guys will definitely find this interesting. It's a graphics system called 1st & Ten.
I remember when they first started using the yellow line on the tv to designate a firstdown (yeah yeah I've been watching football for awhile). I didn't think it would be that hard until a friend of mine told me there's actually quite a bit of computer sciencey fun stuff going on behind the scenes. Here's a quote from the article telling how it works:

Painting a virtual first-down line on a football field is an excellent example of this process. The idea to paint a first-down line across the field on people's TV screens sounds so simple. As it turns out, implementing this is incredibly complex. It takes a tractor-trailer rig of equipment, including eight computers and at least four people, to accomplish this task!

Here are some of the problems that have to be solved in order for this system to work:

* The system has to know the orientation of the field with respect to the camera so that it can paint the first-down line with the correct perspective from that camera's point of view.

* The system has to know, in that same perspective framework, exactly where every yard line is.

* Given that the cameraperson can move the camera, the system has to be able to sense the camera's movement (tilt, pan, zoom, focus) and understand the perspective change that results from the movement.

* Given that the camera can pan while viewing the field, the system has to be able to recalculate the perspective at a rate of 30 frames per second as the camera moves.

* A football field is not flat -- it crests very gently in the middle to help rainwater run off. So the line calculated by the system has to appropriately follow the curve of the field.

* A football game is filmed by multiple cameras at different places in the stadium, so the system has to do all of this work for several cameras.

* The system has to be able to sense when players, referees or the ball cross over the first-down line so it does not paint the line right on top of them.

* The system also has to be aware of superimposed graphics that the network might overlay on the scene.

Pretty awesome stuff and definitely a good read.