"We really wanted to make sure that the stakes keep rising," explains Simon Otto, the head of story who's been at DreamWorks since Prince of Egypt and most recently worked on Kung Fu Panda, which, he says, was a breakthrough for the studio in terms of embracing more daring stories.

"When Hiccup decides to approach Toothless, that becomes the key to the story," Otto adds. "Our total sympathy is with Hiccup and it determines how the third act will play out. That's Chris and Dean's core idea: how Hiccup repairs Toothless and they create this strong bond."

Otto, who worked on the film for three-and-a-half years, says one of his goals was to differentiate each dragon. "We came up with a salad bowl concept for the dragons: it was like that game you played as a kid where you can exchange different body parts, and so Toothless was a mixture of a salamander and a black panther and a bird of prey. The change in director gave us the time to study birds and bats and salamanders and create a library of movements. For the Deadly Nadder, it was a combination of a T-Rex, ostrich and a parrot."

The goal was to distinguish each dragon.

Toothless even fulfills the desire of the audience to recognize their own pets. "For example, 'The Forbidden Friendship,' which is that Black Stallion-like sequence where they first meet," Otto says. "The way Toothless comes down off the rock and wiggles his ears, blinks with eyes and the muzzle movements are all ideas that we see in our cats and dogs.

"Dragons haven't been done in CG-animated movies, so we wanted to be colorful and play with the individual design. The visual language of the movie is based on really strong, caricatured shapes but with very realistic textures and lighting.

"We were able to animate much bigger data with simplified geometry and path tools that allowed us to see where the dragons fly in 3-D space. These little things helped us with the problems that we faced on this film."

Given the time constraints, Sanders and DeBlois wanted to shorten the lag time between layout and lighting and also wanted a more naturalistic look, so they hired cinematographer Roger Deakins (No Country for Old Men), who was previously a visual consultant on WALL•E. However, instead of conducting a couple of seminars, Deakins requested to stay on throughout the production. "From that point on, he worked with both layout and lighting and had an influence on every choice from lenses to camera movement to lighting shots in his naturalistic style," DeBlois explains. "So every frame of our film has a little Roger Deakins kiss upon it."

Every frame has a Roger Deakins kiss upon it.

In fact, Sanders is so comfortable with CG animation that he has no intention of returning to hand-drawn. "We were the beneficiaries on this movie of some gigantic advances in beards and fur and water. A lot of surfaces were brilliantly rendered. There was extra pressure to learn this process because it was something we very much wanted to learn. I think, in particular, Dean and I were interested in moving the camera and changing the lenses. At the same time we were careful to limit what we did with it even during the flying sequences. We wanted the film to appear as though it had been really shot.