Quote Originally Posted by XanBcoo
There could be more, but the one I've read most about was the idea to use small cameras to capture the actors' facial expressions.

Here's a neat little featurette about it: http://www.youtube.com/watch?v=P2_vB7zx_SQ
Really cool stuff, I saw the movie without knowing exactly how they accomplished it.

For anyone who has read Neal Stephenson's The Diamond Age, this kind of technology sounds a lot like the precursor to "ractors." There actors are tattooed with embedded motion capture technology so they can take on any role from the comfort of a small sound stage. The makeup/costume is superimposed over their bodies the same way.

I found the part where Sigourney Weaver and Joel Moore likened this new style to stage acting really enlightening. A good enough actor shouldn't have any trouble with this or even green screens. However, there have been tons of other green screen movies where the acting is horrible, so it really is all up to the caliber of the actor you cast.