Psychological conditions substitute for character development and, to add insult to injury, are abandoned with abandon whenever it suits the filmmakers (that is, whenever those characteristics get in the way of the plot).

And then there’s the problematic combination of photorealistic settings and fish, which are cartoony in design, but whose behavior makes them more like humans in fish suits than fish who can think.

In other words, without a guiding analogy, all the key decisions in Finding Nemo are essentially random, held together by a superficial logic at best. In fact, for a film that takes place in the ocean, it’s awfully shallow.

Perhaps you think I’m being too picky here. What’s wrong, for example, with the fishes’ unfishy behavior? If it’s wrong here, how about elsewhere, like SpongeBob SquarePants? He isn’t anything like a sponge. Is that a problem too?

Well, actually, no. The problem with Finding Nemo lies in the inconsistency of its alternative world and here we can point a finger squarely at CG technology’s ability to make things photorealistic. It worked fine for Toy Story because there the point was to make everything, including the toys, as real as possible.

And SpongeBob also works, because in an unabashedly cartoony world there are no set rules to begin with. So SpongeBob can have whatever combination of human and spongy characteristics the creators choose, as long as they are consistent with them.

But when we include elements that flirt with live action, we give up a degree of license. In Finding Nemo, the backgrounds and effects say real world but the character designs and performance say cartoon and you can’t have it both ways. Part of the beauty of Toy Story, and SpongeBob for that matter, is that there is such coherence between the design, animation, characterization and action. Both precisely define their places on the continuum between reality and fantasy and maintain them in every aspect of the film from beginning to end.

Besen argues that SpongeBob’s style helps sell the combination of human and animal-like attributes. © Nickelodeon.

From all this we can take two key thoughts: to make good films we need internal logic to guide the decision making for every element including the technology, and we need discipline to use the resulting choices consistently and well.

Such issues have always been important to thinking animators. As early as the 1930s, Disney animators began to question the logic of Mickey: how did a three-foot mouse fit in with the rest of the gang, a more or less normally proportioned bunch of cartoon animals? Once they had thought about it, they couldn’t account for the discrepancy.

And as the studio moved into feature films, members of every department would collaborate on the story development phase. From the beginning of pre-production, they would be looking for logical, inventive ways to make every part of the film count as part of the content and ended up with films that were way ahead of their time in their remarkable storytelling techniques.

But talk about discrepancies: now we have animation that looks like live-action and live-action that can be manipulated like animation, as well as all the traditional techniques to contend with. How can we reconcile so many possibilities? There has never been a time when there was more need to understand the real nature of this medium.

A couple of years ago, I was in a planning meeting for an outdoor live-action shoot when the question came up, “How long is the alleyway?” The location scout answered, “15 feet.” As the crew debated how they were going to shoot the sequence in that constrained space, I started wondering how an animator would respond to that question. And then I realized what the animated answer was: As long as it needs to be, of course.