If you want to make a short at Pixar, the studio offers a special program where resident artists — those who work anywhere in the company — have the chance to pitch three ideas to a panel of directors. But “Piper” skipped that step entirely, in part because it grew out of an experiment Alan Barillaro was conducting in his spare time.

“In computer animation, the tools aren’t done yet. At Pixar, we’re constantly asking, ‘What’s the best way an artist can express themselves?’ and I take that pretty seriously, so there’s this whole laundry list I have in my head of how can this tool be more visual,” says Barillaro, who used his free time following “Brave” to see whether he could “sculpt” one of Pixar’s existing bird models into a sandpiper.

“I wasn’t planning on making a short,” says Barillaro, who repurposed a crow from “Brave” and digitally whittled it down to the character he wanted. “This would have stopped as a test,” he says, except he showed colleague (and “Finding Dory” director) Andrew Stanton — a key member of the studio’s so-called “Brain Trust” — his work, and Stanton encouraged his protégé to pursue it further.

Barillo began his career in television animation and came aboard at Pixar 15 years ago to work on “A Bug’s Life.” He didn’t know much about computers at the time and had to learn on the job, working his way up the chain to supervising animator on “Wall-E” — one of Pixar’s most photorealistic films. Visually, “Piper” takes certain cues from that project, which, like “Finding Nemo” and its sequel, was directed by Stanton.

Like “Wall-E,” the film opens on an environment so convincing that we’re not sure whether we’re watching footage captured with a camera or rendered via computer — although Barillaro stresses that every detail of the short, from the lighting to the smallest piece of kelp, is carefully crafted to support the composition. He also followed “Wall-E’s” lead in dispensing with dialogue, relying on Piper and her fellow birds to express themselves via pantomime.

“When I started out, I remember (Pixar president) Ed Catmull instilled not to be impressed by the computer. It’s just a tool, he told us. Make sure you push it and ask what you need from it as an artist,” Barillaro recalls, who pushed Pixar’s software to the max. “The crew told me, ‘Usually you can do water, feathers and sand, but you pick one.’” “Piper” called for all three — and to get the effect he wanted, the bird models had to be rigged with anywhere between 4.5 and 7 million feathers. “If you look at birds, their movement is so deeply rooted in their feathers. That really poses a problem in computer animation,” he says.

The water called for an entirely different solution. Since most animation software has been modeled after real-world physics, the computer is powerful enough to simulate elaborate aquatic patterns. But Barillaro didn’t merely want the virtual water to look convincing; he needed it to serve as a character in his short. To the extent that Piper is afraid of the water, the rising tide would need to be a dramatic foil, and his creative team would need to be able to control the shape and timing of each wave.

The solution? “Brett Levin, our tech supervisor, had this idea of attaching eyebrows all along the beach,” says Barillaro, explaining how Levin adapted the model for an eyebrow — a simple, relatively limited curve shape — to suit their needs: “So the water edge is literally 40 or 50 eyebrows moving back and forth. And the reason is that if we’re talking about comedy timing, it has to be exact to the frame.”

That’s another strategy Barillaro learned on “Wall-E,” along with the idea that great comedians — like the vaudeville stars that inspired him — rehearsed until they got it right. So even if it drove his team crazy, Barillaro would tweak the timing until the moment felt perfect. The fact that the final render looks realistic enough that we could be watching actual birds on a real beach just goes to show how the crew managed to bend the computer to their artistic demands — which, after all, was the point of the experiment that inspired the project in the first place.

“On ‘Piper,’ we really tried to handcraft it, not to let the computer make a decision for us at any point,” Barillaro says, explaining how even the individual grains of sand at Piper’s feet had been individually placed by animators. “You have to stay subversive when you deal with computer animation. You never want to be tricked into the tool doing the work for you.”