"Kung Fu Panda" directors Mark Osborne and John Stevenson are ready for a break. The film, like all animated projects, took years to complete. "We're worn out," Osborne said recently. "We need to get a little objectivity."

Good luck with that. The two talked recently about Panda star Jack Black toning himself down, how directing an animated film actually works and channeling Al Swearengen of "Deadwood."

Q. You guys seem to finally have found the way to best use Jack Black — rein him in in an animated film.

Stevenson: He reined himself in. Jack was the one that really made that choice about how to play Po. Right at the very first session with him, he started to bring out this rather more restrained and vulnerable and insecure and self-aware character. Mark and I had a slightly different idea for Po before he did that. We were thinking that he might be more snarky, tenacious.

When Jack started to deliver the lines in this rather more vulnerable way, it was instantly and very obviously much more appealing. We went about changing and re-crafting the story to support that choice.

Q. Forgive an ignorant question, but what does the director in an animated film actually do?

Osborne: It's more directing more often. It's a really annoying version of directing, because sometimes you're having to say the same things over and over again, because the project takes so long to create.

Stevenson: Nothing in any frame of our film, or any animated film, happens by chance. Every single part of that frame, whether it's the leaves on the trees in the background to the cup and saucer out of focus in the corner, every single aspect of every single frame has been decided on. And not only decided on. It had to be designed and built and animated and placed in the shot.

All of those decisions have been subject to constant review and debate. ... The art is to hopefully not even make people aware of that.

Q. The voice acting in the film (the cast includes Angelina Jolie, Dustin Hoffman and Ian McShane) is quite good. Were you satisfied?

Stevenson: We had really good actors, and that was the reason, first and foremost, that they were cast in the movie. It was not because some of them were huge stars, but when we were working out the story in our minds we saw the characters first.

We had them all designed visually before we did our casting. We just sat down and tried to imagine who in our wildest dreams would be the best actor that we could get to embody the personality traits that we wanted for these characters. ... We were very fortunate that when we went out to all those people they said yes. And maybe one of the reasons that we got such a fantastic cast ... was because we were offering them real roles.

Q. In McShane's case (he plays the villain Tai Lung, a snow leopard), you can detect a little of "Deadwood's" Al Swearengen.

Stevenson: Ian basically said, "I think I'm going to be somewhere between ("Jungle Book" villain) Shere Khan and Al Swearengen. When he got too Shere Kahn he started to be a little too Englishy. We'd say, "Less Shere Khan, more Al."

Osborne: We ended up with Swearengen for kids.