It takes an army to build a Pixar film universe. Just ask Peter Sohn, the director of the upcoming film The Good Dinosaur.

He's been working on the heartwarming movie, which will be his feature film debut, since 2009, when it was originally conceived by previous director Bob Peterson. The film, like many Pixar projects, was born out of a simple question: What if?

More specifically: "What if the asteroid that was supposed to wipe out the dinosaurs 65 million years ago missed?" Sohn explains in an interview with Mashable.

The film aims to answer the question, framing its story around a fearful apatosaurus named Arlo who gets lost and befriends a human boy named Spot on his journey home. It's a tale of survival that flips the classic "boy and dog" narrative. In this film, Arlo is the boy, and Spot is a dino's best friend. Because Arlo is the main character, the design team faced some unique challenges.

"We're trying to make him feel like an 11-year-old kid, but how do you do that with a dinosaur?" Sohn says.

Well, to start, you give him brighter eyes and a goofy expression. Together, small choices like those give the impression of innocence and naiveté, Sohn explains.

A new interactive poster for the film, which shows the wondrous bond between Arlo and Spot, premiered exclusively on Mashable's Snapchat Discover page. Sohn enjoys the app's immediacy, the urgency inherent to a disappearing image or video.

"It’s almost like capturing lightning in a bottle," he says.

One of the film's top challenges was creating a world fit for Arlo, a landscape that was "big enough to make a dinosaur feel small."

"There were great lengths to try to create a natural world that was rich in all its glory," the director says. "We did a lot of research, going out to the northwest — Wyoming, Idaho and Oregon."

His artistic team drew inspiration from those grand landscapes, but also took note of their "dangerous elements" — like landslides and quicksand. In order to recreate the world, the animation team analyzed digital topographic maps created by the U.S. Geological Survey for Google Maps, taking note of the actual altitude of mountains and heights of rivers that would populate Arlo's universe.

They also studied the "millions of trees and billions of leaves that it would require to fill out a world that went for 500 million miles off into the distance," Sohn says.

There's only so much you can do with rendering "before you crash all the computers," he says — which explains why Pixar projects take such a notoriously long time to create.

"There’s nothing to photograph, there’s nothing to put into the computer," continues Sohn. "There are hundreds of artists that help make every blade of grass, every tree, every rock, every drop of water. It’s all meticulously done."

Speaking of which: Water is one of the central design themes of the film, because Arlo has to follow a river to find his way home. But animating that water wasn't easy. It couldn't just run alongside Arlo throughout the film — Sohn wanted to give it an "emotional" current, so to speak. For example, when Arlo is having an internal struggle, the water is roiling. When he's enjoying nature or connecting to his new friend, the water "would be calm and glasslike."

"There was a lot of work in trying to make that connect," Sohn says.

The end result, he hopes, is a setting that's "beautiful and threatening at the same time."

After working at Pixar for over 15 years in various departments on films like Up, Finding Nemo and Ratatouille, Sohn has seen the company change and grow into a behemoth of animation. And though its tools have changed and its teams have expanded, its philosophy has never wavered.

"That always has remained the same since I’ve been here…the philosophy of trying to make the best thing possible," he says.

The Good Dinosaur will hit theaters Wednesday Nov. 25, the day before Thanksgiving.