Here's an excerpt on their discussion of 3D:
Martin Scorsese: I found that the setting of the story lent itself to using the element of space and depth. It had a lot to do with the machinery of 3D, which creates something beyond itself, the movies that could bring people together. They create images that go up on the screen, and once they're experienced, they're gone. But the emotional impact stays with you.
James Cameron: I found the film to be very emotional. I felt like the audience was right there with the nuance of every moment.
Scorsese: What happened is that, rather than 3D being used in a way that I used to enjoy, too -- with the camera flying around -- I was trying to take the audience and put them in that world. And bring the children forward. Because seeing the kid [actors] every day first thing in the morning, I'd grab them and hug them and kiss them. And that's what I wanted the audience to feel like.
They went on to talk about how 3D brought the audience closer:
Scorsese: We discovered it. That's what we felt, saying, "Why's it better this way?"
Cameron: But the beauty of what you did is that you reacted to the 3D instinctively. You saw it and you said, "Oh, I can do this, and I can do that." You weren't waiting for some 3D guy to tell you what you can and can't do.
Scorsese: That was the key thing. It was [DP] Demetri Portelli was really good on the I/O. Intraocular -- that's the lens for the right and one for the left. And if you take it too far apart, that hurts. You would hear me scream., and [3D stereographer]
Cameron: We made up a term: "brain sheer."