I've spent a fair bit of time over the last couple of weeks learning about creating chroma key video. I've been really slammed of late, and most of my play time has been carved from when I might normally have been sleeping. My goal was to mix some Second Life machinima with some real-world video. It's been fun to learn, and where my first effort is rather trivial, I did learn some things that I will be able to put to use on more practical projects in the future.
I started off trying to create this using green backgrounds. I basically created a big box in the sky with several 10x10 panels that I had turned green. It was a lame attempt to emulate green screen production techniques. The problem was that the side walls and the floors, even though they were covered with the same color of green, were presented in Second Life with shadows. So I was dealing with two different shades of green. Where Final Cut could handle the two different colors it was still mostly a pain to have to use two different filters. There was also a lot of green in the avatar's skin, and after playing with the skin color it was still difficult to get good results. I tried several things to get around the problem with the raw captured video. I tried completely closing in the box from any ambient light (is there such a thing in Second Life?), but that didn't solve the problem either. What finally worked was to not use green at all, but to use black. It was too easy!
Here's my video... I'm afraid to publicly admit how long I spent making this. It took a long time! I am gradually getting faster and smarter with Final Cut. It's been a lot of fun, but I still have a long ways to go.