Breathing life into dragons

You've probably read "Harry Potter and the Goblet of Fire" and maybe you've even seen the new movie. Harry, the boy wizard, competes in the Triwizard Tournament, facing merpeople, dragons, and his archenemy Lord Voldemort.

Each scene in the movie is carefully crafted to seem magically "real," so the audience can lose itself in the world of Hogwarts. Creating a film as high-tech as Harry Potter can take a year or longer.

One challenge in "Goblet of Fire" was to make a believable Horntail dragon that remained true to author J.K. Rowling's vivid description: "She writhed and twisted, furling and unfurling her wings and keeping those fearsome yellow eyes on Harry."

To create this dragon, Mike Newell, director of the film, called on the talents of Industrial Light and Magic (ILM), the special effects branch of Lucasfilm in San Francisco. Lucasfilm is known for its Star Wars series, but ILM has worked behind the scenes in many movies, including the past three Harry Potters.

For more than a year, a team of special-effects creators, led by Tim Alexander, worked hard to design the flying, fire-breathing Horntail dragon that we now see on screen.

"Goblet of Fire" was mostly filmed in Britain, so the dragon was first designed by Warner Bros. studio's art department in London.

"They do a bunch of drawings, different styles, different head and body shapes, until they have the one they like," Mr. Alexander explains. "Then they make a 'maquette,' which is basically a physical three-dimensional model."

The dragon model is smaller in scale than the dragon in the film, but it's still pretty large: It was shipped to ILM in a crate that was big enough to hold a car. "The [dragon's] body had wings that folded out; the tail popped off," Alexander says. The wingspan of the model is more than 14 feet, the length of a minivan.

Once the dragon model was put together, the design team could see how they needed to "construct" the dragon in the computer.

The first step was to photograph the model from every angle to gather details about its color and texture. They also made a 3-D scan of the maquette.

"The scan is like a laser beam. It tells the computer exactly where the surface of the dragon is," Alexander says.

After the scan, creators stored the shape and proportions of the dragon in the computer. They created the dragon's basic framework. Then it was time to add the details that would make the dragon look - and act - real.

Work was divided into two areas: "painting" the digital dragon's color and texture and developing the creature's movements.

One person worked on "painting" the dragon for 12 weeks, Alexander says. The painter programmed the details about the dragon's surface into the computer - bumpy and smooth areas, where it needed to be reflective, wet or dry - and created different dragon "looks."

At the same time, creature developers worked with animation director Steve Rollins to figure out how the dragon should move: How would it fly? How would it move if someone grabbed its leg?

For this, Mr. Rollins researched the real movements of birds such as owls and albatrosses, and also bats.

"When you see the movie, look for the head twitching, head cocked, and quick twitchy movements; these were all from the bird references," Alexander says.

Figuring out the movements took a few months. Rollins worked closely with Jimmy Mitchell, the visual-effects supervisor with Warner Bros. in London. Mr. Mitchell talked daily with Mr. Newell, the director. The dragon computer file could be played in London and San Francisco at the same time. Using the Internet like a telephone, they could discuss their ideas, changes, and how the next shot in the film should look.

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