The big effect in The Unborn is revealing characters as they become possessed. Courtesy of Asylum FX. © 2008 Rogue Pictures.

When it comes to eliciting oohs and ahs with vfx, broad strokes tend to do the trick, but to really scare an audience is another matter entirely. That's one of the key principles behind Nathan McGuiness and Mitchell S. Drain's approach to The Unborn, on which they served as visual effects supervisors through the Santa Monica-based effects house, Asylum Visual Effects.

"A lot of movies I've worked on have giant monsters stomping down the street or giant spaceships or that kind of thing," says Drain, "Myself, I'm a horror movie buff. For a lot of horror movies these days, it's more about gore and about limbs being cut off and about being tortured than it is about the subtle scare... To me, subtlety is the real art of visual effects."

McGuinness and Drain began working on the project early last year, as the film was still in pre-production, giving him plenty of interaction with writer/director David S. Goyer (whose credits include Batman Begins and all three Blade films, the last of which he helmed as well). "That's where Asylum kind of came in and, even before principal photography, we shot some tests of our own. Some video tests of some of the folks at Asylum going through this possession and basically just showing David what kinds of effects could be done."

Asylum was well-suited to handle any of the potential vfx work that Goyer required. "We'll start with storyboards and concept art as needed by the client. We have our compositing departments, matte painting and texturing departments, tracking, animators, modelers, riggers. We have fluid and effects animation specialists. We run the whole gamut. All those departments came into play in different ways throughout the project.

Working with Goyer was a delight for McGuiness and Drain as the team was able to confer with the director about what would be called for in each shot at a very early stage, allowing them to get what they needed from day one. "I think that [writer/director] paradigm worked very well. The fact that he wrote the script, he had already seen the movie play out in his head. Everything worked very efficiently because he had a vision, which is absolutely crucial.

Drain also cites Goyer's confidence as a director in terms of the effects. "There was no 'let's try it this way' or 'let's try it that way.' It was, 'Here's the shot. That's how we're going to do it. Let's make it happen.' We went into principal photography in March very prepared. Everybody knew what they had to do and how to get it done. It was a very efficient working process.

The more-involved 3D effects helped to achieve the photoreal look required to scare the audience.

Part of the way Asylum works is that departments can expand and contract as needed. "At any given time we had maybe three to five animators going. Maybe six compositors. A couple of matte painters. A couple of trackers. It wasn't a huge team because it wasn't a huge job in volume. It was really more of a conceptual job... It's the kind of project where we just tell the artists, "Well, we've just gotta do it the hard way." There's no easy way to achieve some of these effects. We've just got to get in there and roll up our sleeves. It might be a small team that does it but it's very intensive work.

One of the challenges of the entire film was finding visual cues to let the audience know when characters have become possessed. Oftentimes, the effect was achieved with practical blue contact lenses that the actors would wear on-set and which could later be subtlety modified with CG. "If you have the blue eyes, then the black iris expands and contracts in the light and all that sort of thing. In a lot of the shots we took the iris and made it just a pinhole, which is something that we couldn't have done in-camera with the contact lenses because the actor wouldn't have been able to see through them.