How Football's Magical Yellow Line Works
Technology Keeps Everyone in the GameBy Robert Cong
Product Marketing Engineer
Are you ready for some football? The latest lockout antics are ancient history, pre-season brawls are over and America's number one sport is back in action. Football uses a lot of interesting technology that we take for granted, and in this article I'll answer the question "How the heck do they get that yellow first-down line on the field?"
It may seem like a simple task, but like all computerized animation, it's a lot harder than it looks. When it comes to action films, most people have heard of CGI (computer generated imagery). I think Terminator, Avatar or the Old Spice commercials. But I would argue that no other example of CGI is as important as that yellow first-down line on my TV screen once Sunday kick-off time comes around.
How It's Done – By the Electronic Chain-GangRemember the suspense of waiting for the chain gang to run out onto the field to measure for first-downs? Now we typically know the outcome long before they've figured it out on the field. What is less understood is how much work goes into setting the system up before any players step on the field.
The process begins by creating 3D models of every field at the beginning of the season. They're all different and thus the system must factor in subtleties like pitch and positioning. The second bit of technology are tracking devices attached to all stationary cameras. Each tracking device records every minute camera movement, tilt, zoom and pan, and reports this information in real time. This position is recalculated 30 times every second! On game day, the computer system integrates the position of the cameras on the 3D computer map.
The third piece of technology is the color separation process. This requires building immense color palettes in the computer prior to the game. One palette contains all the possible colors of the field (all the shades of the grass, sidelines, logos on the field, etc.). The other palette is the colors of everything that will be on top of the field (players shoe colors, uniforms, referee uniforms, skin colors, etc.). Everything from one palette goes under the line and everything from the other palette goes over the line. Poor weather conditions can create havoc with the coloration process. Think about snow or mud, mud on the ground versus mud on player's uniforms...simple?
What it Takes – Gigabytes Plus Man-PowerAs you might guess, the virtual first-down line takes some major giga-drive power: four SGI computers, a PC, three special computers used in conjunction with the television cameras shooting all the action on the field, and at least four human beings to run and perfect the system over the course of the game. In order for the line to look clear and precise, the entire system must keep track of a long list of items: the orientation of the field with respect to the camera, the location of every yard line, every perspective change from the camera's movement, when players and referees cross the line so they are not painted over, superimposed graphics from the network, and much more. While the concept of painting a yellow line across the screen seems simple enough, the technology is anything but simplistic.
Now you can amaze your friends at the next game-day bbq when someone says "How do they get that yellow line on there?"
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Robert is a graduate from Cal Poly, San Luis Obispo in Electrical Engineering. His interests include sports, movies, music and playing with cool, new gadgets.