The Illusion and Emotion Behind 'Toy Story 4'

The phenomenal success of Toy Story 4—No. 1 at the box office since its opening two weeks ago, with a worldwide gross of more than $510 million to date—is fueled by the wizardry of Pixar Animation Studios, which continues to push the limits of computer-generated imagery (CGI) 23 years after the original Toy Story was released.

The first movie in the series, which came out in 1995, was the product of technological limitations. Toys are geometrical, plastic and kept indoors on flat surfaces—the simplicity of their shapes and textures made them perfect subjects for the first feature-length movie consisting entirely of CGI. For the latest film, the creators found that the challenges are becoming more philosophical than technical.

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Toy Story 4 opens in the past, revealing how Bo Peep (Annie Potts) was separated from the rest of Andy's toys before the events of 2010's Toy Story 3. Set during a torrential downpour, the sequence opens with Woody (played by Tom Hanks) leading a rescue mission into the sewer to retrieve RC, and ends with a tearful goodbye. Water is computationally intensive—especially thousands of individual droplets of water—but just as remarkable are the tiny details that make human emotion legible on the Toy Story characters' faces. Eyebrows are precisely posed, the corners of mouths crinkle with emotion and nostrils flare.

"The characters in Toy Story 4 actually breathe—you can see their chests moving," global tech supervisor William Reeves told Newsweek.

Where previous computer animated movies could cite concrete metrics—like the millions more difficult-to-render hairs that Sully (played by John Goodman) sprouted between 2001's Monsters Inc. and 2013's Monsters University—technology has advanced to the extent that Pixar's challenges have become more subtle, as they pursue what Reeves calls "the illusion of life."


Reeves was instrumental in the 1980s development of RenderMan, a suite of computer animation software (now in its twenty-second version) that has become the industry standard for visual-effects driven movies, from Avengers: Endgame to Terminator 2: Judgement Day.

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Computer animation begins with what Reeves calls "geometry," similar to the polygons comprising a video game character. Creating geometry is building a world of points, which describe shapes. Those shapes could be a character, or an object in the environment, or the environment itself.

The next layer involves software known as a "shader," which applies material properties to surfaces. While color and texture are self-explanatory, other shader elements—many developed at Pixar—were once massive innovations in the field, such as the subsurface light scattering that makes biological textures like leaves and skin more realistic by calculating how far light penetrates beneath each type of surface.

Rendering a single frame of Toy Story 4 required between 40 and 50 hours and a network of 55,000 computer cores. The original Toy Story used fewer than 300 cores. But the number of cores is a measure of more than just raw computing power—they can also render multiple frames in parallel, like multiple virtual "teams" dividing the work.

RenderMan can now handle many tasks automatically, like reflections on shiny surfaces, that were once tedious and time-consuming to create. Sometimes the software works too well.

"In fact, what happens is, sometimes you get reflections you don't want. You have to dull it up," Reeves explained. "Real physics would say, 'Yes, there should be a reflection there,' but from an aesthetic point of view, maybe you don't want that."

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Animation advancements aren't just avenues to greater realism; they also offer new storytelling opportunities. Animators can lean into lighting and other advances to create subjective effects, like the subtle green light applied to Toy Story 4's creepy doll, Gabby Gabby (played by Christina Hendricks) to underscore her villainous intentions. A sequence set at a carnival involves 30,000 animated lights, any of which can be manipulated individually to achieve whatever effect an animator might pursue.

Before Toy Story, Pixar pioneered computer-generated imagery in shorts like Luxo Jr. and 1988's Tin Toy—the first CGI film to win an Academy Award. But tackling a feature-length film was monumentally more complicated. Pixar Animation Studios, then an independent spinoff from George Lucas' Industrial Light & Magic, already had an early version of RenderMan, but they didn't yet have the animators, technical directors and infrastructure necessary to tell a feature-length story.

"It's not a short anymore, it's not five minutes long. You couldn't go to a whiteboard and write down: 'Okay, here's the 20 shots in our short,'" Reeves recalled to Newsweek. "Because we were green, we didn't know what we were getting into when we started."

Pixar ballooned to 129 employees as production on the first Toy Story got under way, including 27 animators. Along with production hurdles, including a radical rewrite of the movie in 1993, the company was soon confronted with a bevy of technological and aesthetic obstacles. "How do we do hair? How do we create realistic or believable humans? How are we going to do joy?"

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While Pixar has conquered both hair and humans, capturing emotions is an ever-evolving challenge. After characters are placed and posed in a shot, animators begin a laborious polishing process under the supervision of Toy Story 4 director Josh Cooley.

"We probably spend about 10 times more time polishing a shot than they did back on the first Toy Story," Reeves said.

As computational power allows greater attention to detail, more nuance can be brought into every performance, right down to the precise pose of individual fingers. Pixar may have created Woody and Buzz because they could bring toys to computer-generated life more easily than humans, but advancements in CGI have made capturing the "illusion of life" about more than photo-realism.