[cclogg]

Yeah totally, having some experience with 3D motion tracking and green screens, I was thinking: wow, it's so smooth and so perfectly tracked, AND cuts between player/grass so well. I know how finicky it can be to key out elements, so it is quite amazing that whatever algorithm they have in play can do it so well (is there a jersey color that's close to grass color lol? Wonder what the edge cases are).

[halisaurus]

It's alluded to in the article that outdoor fields and green jerseys are the hardest. For outdoor fields the lighting is affected by the time of day, cloud coverage, players moving along the field, and plenty of other things I'm sure. It says they spent a lot of time creating a unique palette for the fields and that domed stadiums were preferred by the engineers on site. Indoor lighting probably reduced the shadows a lot.

[baddox]

I wonder if they use any tracking technology that looks at large groups of pixels over time. If you could track a player as a closed shape moving through space, you could mask out that player from the background even if pixels on the player's uniform were identical in color to the field's palette.

[nmjohn]

There are many teams that have very similar jersey colors to grass. Moreover, what is even more impressive, is there are some astroturf fields that aren't even green [1]! And the first down line works just fine on that as well.

[1]: http://upload.wikimedia.org/wikipedia/en/5/56/Bronco_Stadium...