"We had to make sure we could cut very precisely back and forth from visual effects and live-action character," Johnson adds. "So we found that the projected texture technique essentially gave you 75% of the real dog and, when it broke down, we had to put in very accurate muzzles, teeth, eyebrow area, depending on what the animation requirements of the shot were to bring the two things together. No two shots are the same so you have a toolkit that allows an artist the freedom to cherry pick which bits of the shot are going to be texture or which bits are going to be CG fur and make the shot as convincing as you can based on what the real dog is doing."

Meanwhile, Rhythm & Hues created 100 + shots, 80 of which were CG dogs. But this hybrid approach with so many characters was a far cry from Garfield, Scooby-Doo or the upcoming Yogi Bear. "We had to change our strategy to make it more photorealistic," concedes Mike O'Neal, Rhythm & Hues' visual effects supervisor. "They weren't going for a chipmunk movie with a handful of characters based on a popular cartoon. They wanted it to feel like real animals. Even our all-CG shots had to be photoreal. They wanted people to think that that's a real dog on a surf board.

"That changed how we rigged the face, a lot of the modeling," O'Neal adds. "We had to do extra controls to the head to shape it more like the actual dogs in the scene. Little things like getting the collars to stay outside of the fur ended up being a huge task because there are so many dogs and so much memory and so much information being passed from stage to stage. A lot of controls had to be added after the fact in our technical animation stage just to be able to handle collars flipping; every collar has a simulation on it so the tag is moving and pushing down the fur; all the fur is moving during the dance sequence, which has 40 dogs.

Still, there were some inherent challenges in putting photoreal-looking animals in outrageous situations. "There are moments when you jump over the line in trying to make it funny where you can still make it look like it's photoreal," O'Neal suggests. "In the dancing videogame sequence, for example, the idea was to sneak up on the audience with it. So you start with an actual dog standing on a machine, and then you go to our photoreal CG dog doing very realistic dog-like dance steps. And slowly with each cut we gradually go more over-the-top. So by the end of the sequence you see him doing things that no dog could ever do like dancing on his head."

The surfing sequence was additionally challenging because of the CG water. "We had done fluids and oceans before in your more action comic book kind of movies, but we never had to do it in a photoreal setting with a photoreal dog and to have breaking waves and white water and that level of complexity," O'Neal says. "We used Houdini for the water and Mantra to render it. The surface of the water was a straightforward grid with a lot of animation controls on it. But then every little part of the water where it needed to break and shoot off and turn into white water and foam required extra pieces. Any time the surfboard touched the water and created a wake, it had to be simulated and matched back on and rendered into the system.

"The movie is all about perception," O'Neal maintains, "so even if the dog matches the dog in the previous scene, if there's a camera angle that looks like it doesn't match, then you have to fix it: making eyes bigger, making eyes smaller, shortening the nose; lengthening the nose. We had to do a lot of things that normally you wouldn't worry about with a regular animation set up."

Bill Desowitz is senior editor of AWN & VFXWorld.