PCW: You mentioned using blue screens. Did you need to use blue screens because Kermit the Frog is about the same color as a green screen?
Ivins: Basically. Characters with blue on them were less problematic to pull keys for, and there aren't that many principal characters that had any blue on them at all. Gonzo has some blue feathers on his head, which was a nightmare, but other than that, blue isn't in the Muppet palette very much. There are a couple of Muppets that appear in the arches shots that are blue...
PCW: Sam the Eagle!
Ivins: Right--he was shot on blue screen, believe it or not. It really wasn't a big problem. But Kermit on green screen is a disaster!
They shot tests on blue and green, and sent them to us, and we pulled keys on them. They didn't want to carry around a green screen and a blue screen, or make a green stage and a blue stage, so in the end we just decided on blue as the less problematic color.
I didn't realize before the project how many Muppets are hairy and furry. They are furry! And that is not friendly to blue screens. That ended up being the most challenging thing about it--the intricacy of getting fine detail in hair, you have to pull a key that's very specific to it. If the character is lit brighter on one side than on the other side, or if there's shadow down by the legs or whatever, the key has to be different there. So a lot of times, there are multiple keys on each character, basically.
And the puppeteers in blue suits, they're not lit very well if they're behind a character, so you have to do a lot of rotoscoping and luminance keying to fix those things.
PCW: Were the puppeteers always controlling the Muppets from underneath, or did it depend on the specific scene or Muppet?
Ivins: For most of the project they were [underneath], but there were quite a few head-to-toe shots of the Muppets. For those scenes, puppeteers were in the shots, because it sometimes took four puppeteers to make them walk and move their arms and their head. It was quite an undertaking for the puppeteers to stay behind the puppet and get the right form of motion and everything. For those head-to-toe scenes, the [characters] were shot on a blue-screen stage and composited into the shots later.
They ended up building several pretty involved rigs--in one scene in the movie, Beaker gets shrunk down to about 5 inches tall, and we see him from above, running in a circle. To puppeteer that, they basically built a merry-go-round with a platform about 4 or 5 feet off the ground so that they could have puppeteers control him to run around in a circle while somebody spun the whole thing around. They went to great lengths to compose some of these shots.
Sign up for Computerworld eNewsletters.