Peter G. Travers knows his digital effects: he's worked on the first Harry Potter, The Lord of the Rings and the Matrix, and most recently supervised many of the key effects sequences on Watchmen. We spoke to Travers about the movie's most difficult visual challenge --creating a realistic Dr. Manhattan -- and talked about the future of synthetic characters more human than human. (Correct: he also worked on Blade Runner: The Final Cut.)

What was the biggest challenge of the visual effects on Watchmen?

Well the main one was Doc [Dr. Manhattan]. That was the biggest challenge, but we knew that up front. So we certainly dedicated a lot of time to making that work. A lot of it's just about providing an environment where you can create good CG -- when you have CG that you're uncomfortable with, it's typically because the environment is not right. With Doc we knew really early on that that's the thing we needed to focus on, so before we started shooting a lot of planning went into how we were going to shoot Doc; and all of that just tremendously paid off in the end. Without that, if all we were being handed were plates with nobody in the scene, it wouldn't have looked nearly as good.

Because Billy was actually in the scenes, on set.

In almost every single shot -- like, about 99 per cent of the shots. There were a few shots where he was gigantic where we had to make it up -- Billy couldn't scale himself, which was fortunate for him [laughs]. But almost every shot -- and any interaction. That was the trick of the whole thing. There's something in that you're getting the actor Billy to act within the environment; you're getting the actors to react to him. The real trick with all of it is the light suit we developed for Billy, so that he could cast light into the scene and that light would change as he moved. He literally had 2000 LEDs sewn on to his suit. It kind of started as a motion-capture suit, and then Company Global Effects sewed in the LEDs from helmet to gloves to the rest of the body to the soles of the shoe.

So the light would reflect on the rest of the scene?

Yes. In particular, there are some key moments, like the love scene with Silk Spectre when he replicates himself, where you can actually see when his hand is moving across her face. It's like with anything with light in the scene -- even if you're not physically seeing the light source, you're seeing what the light source is doing.

There were early -- probably silly -- rumours that Manhattan's underwear was added. Did you have any concerns with the nudity of the character?

Well, it's the way it was written by Alan Moore, in that the character's losing his touch with humanity. At first he wears a kind of body suit and then it turns into shorts, and by the end he's walking around completely naked. It's like, if a character's losing his touch with humanity, would he even care about wearing clothes? It's a tough thing for an American audience to deal with. In America, we're completely fine with people's heads getting blown off, but the minute we see naked genitalia we have a problem with that. So it was a tough call, I think, whether people would embrace it or not -- but the whole thing was that it was important to the character; to say, "If Superman had really existed, what would he really be like?"

Did you consult with Dave Gibbons on the visuals?

Yeah, he was there on set, but not every day. I guess it's a little unfortunate that Alan Moore rejected it because I think Zack actually did a really good job of replicating the comic book. Zack really got what the story was about, so it's surprising that Alan Moore kind of rejected the whole thing -- but I think he got burned on other movies.

Looking over your CV -- you've worked on Spawn, the first Harry Potter, The Two Towers, Matrix Reloaded -- what do you think has been the major change in CG during that period?

The major change is that we need to do a lot more for less. I think budgets have gotten a lot tighter than what they were, and in a way we have made it harder on ourselves by coming up with these advancements and always succeeding and I guess it's almost treated like, "Oh it'll be fixed in post and you guys will make it work". But I can see that the one thing for Watchmen that was kind of a reminder to me was that the set up makes or breaks the CGI in the film. If you don't get what you need from the environment -- whether it's a big effect or a character -- it's not gonna work.

It's like with Dr. Manhattan. To me, the digital human, there's a lot of technology out there that's been there for a little while, but it's gluing it all together and giving yourself an opportunity to put it all together to make it work. There's so many different aspects to Dr. Manhattan: we put peach fuzz on him, we had to put hair all over his body and in most shots you wouldn't see it -- 'cause I'm talking about the little tiny hairs, like even on a man's cheek. When you light someone in a movie you light them in this kind of three-quarter back-light and you get this bright rim on them. Well that rim on a person's skin is activated by a person's hairs that the light is reaching, even though the skin isn't getting the light. So we're like, "Let's put it on Doc and see what it does" -- and after doing some before and afters with him being absolutely hairless and then with a little bit of peach fuzz, it was like, well, the peach fuzz makes him look that much more real.

Next: resurrecting The Crow, cloning John Wayne and locking lips with Harrison Ford -- the future of digital actors.