How Pixar's character movement evolved from 'Toy Story' to 'Soul'

• Pixar gets its characters to move by giving them an inner skeleton called a rig and filling it with controls that allow for unique and nuanced movements.
• Movies like "The Incredibles" gave animators the ability to convincingly move human muscles while "Coco" let them beautifully animate guitar playing.
• In "Soul," innovative new hand controls and a digital piano rig let the character Joe Gardner play piano in complex and realistic ways.

Following is a transcript of the video:

Narrator: This is a shot from Pixar's latest movie, "Soul." Even though it's animated, everything about how the fingers float from one key to another to the small details like tendons moving in the hand feels just as real as the reference footage that inspired it. While Pixar has used reference footage since the beginning, it could not have pulled off a scene with movement this nuanced and realistic back in 1995 for "Toy Story." And it took years of technological breakthroughs. So how did Pixar get here?

First off, they have an army of animators and riggers. We talked to seven who worked on "Soul" to see how far Pixar has come. Let's start over 26 years ago with the technology built for "Toy Story."

Getting a given character to move starts in Pixar's rigging and modeling department.

Mara MacMahon: Whenever you're thinking of a character model before it's rigged, it's in a completely neutral pose. There's no expression on the face. The arms and legs are all straight. And so the controls that we put in in rigging lets parts of the body move like you would pose like a doll or a puppet.

Narrator: To get a clearer idea of the basics, let's start with this character model of Woody. The rigging department will add the rig, which is essentially an inner skeleton. Throughout this rig you can see all these controls called animated variables, or avars, which animators use to make different parts of a character move around. This early version of Woody had 596 of those controls, which may seem like a lot, but by 2019's "Toy Story 4," Woody had more than 7,000. To make things a little more complicated, one control point is often connected to other control points. So moving one in the eyebrow will move the wrinkles on the forehead. Adding more controls to these "Toy Story" characters would have let them move with more nuance, but back then, Pixar was making a brand new rig for every single character. That would change with "Toy Story 2."

Pixar introduced Geppetto, later updated to Presto, which allowed animators to reuse and adapt rigs for multiple characters. This sped up the animation process and gave animators more control over movements and facial expressions. The new software provided a template of two-legged and four-legged rigs that could be altered depending on the specific needs of a character. According to rigger Jared Fong, the sea lions in "Finding Dory" were actually constructed from dog rigs, with legs folded into flippers. More control with Geppetto also meant more expressive facial movements, as seen in 2003's "Finding Nemo."

To really nail the character's emotions, animators used reference footage. Now fish don't have eyebrows or eyelids, but eyebrows are so important for expressing human emotions. So animators decided to add eyebrow-like lumps to characters like Marlin and Dory. And replicating real facial expressions meant connecting more control points with each other. You can see that with Dory. The control points around her mouth are connected with her eyes and her cheeks, giving her a more believable smile. A smize, if you will. After making major strides with toys and sea creatures, the most daunting challenge was yet to come: humans.

Mr. Incredible consisted of 426 primary controls, 111 secondary animation controls for more subtle movements, and 1,061 modeling controls for sizing and other adjustments. Thanks to Geppetto, the rigging and modeling team could perfect Mr. Incredible and then reuse his rig for other characters. And to really make his movements realistic they used full-body reference footage. For example, this clip where an animator lifts up this exercise ball was helpful for moments like this, where Mr. Incredible lifts up an Omnidroid. And the team didn't animate just a rigid skeleton. On top of the skeleton was a layer of muscles, which could bulge and flex. And the skin on top of that would need to respond realistically. So Pixar developed a new system called Goo. This allowed the animators to see the skin and muscles react in real time as they worked, allowing for greater flexibility and movement and more control over how humans move. Goo led to breakthroughs in moving more challenging body parts, like the shoulders, which were more primitive in earlier films.

Bobby Podesta: The Buzz Lightyear shoulder's a ball and socket. Woody's shoulder is just a stitch line. He's got no shoulders, right? That arm just hinges. Mr. Incredible has a big old strong shoulder. How you get a trapezius muscle there in the shoulder, and how it moves in the pectoral, really complex stuff.

Narrator: The rigs built for "The Incredibles" were designed to let the characters stretch further than the average human. Which was important for Elastigirl, who needed to transform into all shapes and sizes. And just like how superheroes needed to react to forces like gravity, so too did the cars in Pixar's next feature, "Cars."

Pixar extended its technological boundaries yet again with a system called ground locking, which made sure the cars always stayed on the same path, regardless of terrain, without animators having to move them frame by frame.

Bobby Podesta: We had to have our characters be able to follow the contours of the ground without having to animate them, like up and down if it was like, a rolling hill. So it's going to move along these things. And then we're going to animate on top of that.

Narrator: Because of ground locking, Lightning McQueen could now drive smoothly on a flat road that turns into a very windy path automatically. This may seem like a specific advancement just for the "Cars" movies, but it would be important for some of the most memorable characters in "Soul."

By 2007, animators could have up to 150 controls in the human face. So they could give characters a much wider range of emotion. Perfect for a movie like "Ratatouille," which is largely set in the human world. All these intricate controls allowed for the complex array of expressions seen on Chef Skinner. Look at how far Chef Skinner's mouth extends as he's yelling at Linguini. According to supervising animator Mark Walsh, the tech wouldn't have been able to handle such a stretch in "Toy Story" or "Finding Nemo." The groundbreaking muscle work in "The Incredibles" allowed animators to give Linguini more spontaneous movements in the scenes where he's controlled by Remy in the kitchen.

By the time "Toy Story 3" came out in 2010, Pixar's animators had gotten such precise control over how characters move, that it's surprising they'd want to take a step backward. But they actually relied on fewer controls to better replicate the trademark toy movements audiences knew and loved.

Jared Fong: If a character has a limited range of motion in its shoulder, what we'll do is we'll basically lock off some of that range of motion, and then that forces you to animate it in a different way.

Narrator: They still had room to pick and choose what they would keep about the old characters and where to elevate them. For example, they could have put 25 controls in each of Buzz's eyebrows, but decided to keep them simple, like when he had just three per brow in the original, while also giving Spanish Buzz these complicated flamenco-like moves. There was one particularly hard toy to animate: the octopus named Stretch. Despite the innovations in stretchiness from "The Incredibles," making eight tentacles stretch and curl was still a daunting task.

Bobby Podesta:We're fighting against the computer. The computer wants to make things that are that are solid and that are perfect.

Narrator: But it was a challenge they would eventually master in "Finding Dory."

The hardest part of an octopus to replicate is the tentacles, which need to bend, curl, and unfurl. You can see early attempts at this with Stretch and this octopus-like monster all the way back in "Monsters, Inc." In "Finding Dory," Hank also needed to move around quite a bit and grab onto things, like this coffeepot. Hank also had more than 350 suckers combined on his tentacles. Those were so unpredictable that they had to be simulated, a process where movements are automated using code, like with strands of hair and clothing. The tentacles themselves were so dynamic that when one moved it would move other parts of Hank's body as well. And animators used an altered version of this tentacle rig on Dante in "Coco," giving the dog a long, twisty tongue. You can see it grab onto objects here in the short film "Dante's Lunch." But the biggest challenge for "Coco" was music.

Pixar had to figure out how to get Miguel to accurately play guitar. So they strapped GoPros directly to guitars, giving themselves the closest possible angle. They would listen to the guitar music and mimic the exact finger and string movements. It looks so authentic. But Pixar found it could push this even further and make playing music look even more real in 2020's "Soul." As with previous Pixar films, some assets were reused from "Coco." For example, the same rig built for the "Coco" guitars was repurposed for Miho's bass.

Jason Davies: We modified it for four strings and just kind of repositioned it to work for that. For the scenes where Joe plays piano, they went far beyond just matching the music directly to audio.

Narrator: For reference footage, Pixar captured Jon Batiste playing piano at multiple angles. Then, character technical director Jason Davies and the rigging team built a piano rig, which functions like a digital piano. Davies fed the audio files directly into the rig, and the piano would play automatically in time with the music. If a key lit up blue, the animators would place Joe's left hand there, and his right hand would be placed on any key that turned red. They also tried developing a simulation for Joe's piano playing, but it proved tricky, as his finger was too heavy on the small piano keys. So Davies developed a finger contact rig similar to one used on "Coco." Just like in "Coco," where fingers moved the strings on guitars, Dorothea's fingers could play the saxophone, and most importantly, Joe could play the piano.

Jason Davies: When their fingers would intersect the space where a key was, so it pushes down into the keyboard, it would calculate the proper angle that that piano key needed to rotate to make it look like he's pushing it.

Narrator: While the piano played on its own, the hand still needed to capture the complicated motions of playing. Which is why Joe was equipped with 292 controls in each of his hands. That's about half the amount of controls in Woody's entire body in the first "Toy Story." The riggers added variables to Joe's hand that they had never used before. According to character model lead Mara MacMahon, the team even added a control for each tendon in Joe's hands.

Mara MacMahon: So that was something that could kind of capture the tension in his hands as he's playing the piano. So there's a control for each hand, just to make a tendon appear if the animator wanted to really, like, emphasize that particular pose.

Narrator: These state-of-the-art hand and wrist controls weren't just useful for playing music. They also allowed for flexibility. Like Linguini in "Ratatouille," Joe is tall and lanky and has a lot of frenzied movements that had to be highlighted in scenes where he is inhabited by 22. For all of this, Joe had 477 controls in his face and 789 additional controls throughout his entire body, giving him 1,266 controls total. Conversely, they limited the movements on Dorothea to show her regal stature. They even went as far as removing subtle blinks and nods.

MontaQue Ruffin: It's all in like, the look, you know. How they hold their head up, or how they just set their gaze upon whatever they're looking at.

Narrator: But sometimes it's the simplest-looking actions or characters that prove the hardest to control. Take the counselors. They look like simple 2D lines, but they were the most complicated characters to animate.

Bobby Podesta: Doing the counselor characters for "Soul" was pushing our limits of what we could do. And they turned out amazing. That's building on 25, 26 years of history to get to that point.

Narrator: Terry consisted of around 300 controls. A new tension control allowed animators to sharpen or add an angle by assigning it a higher value. This allowed Terry and the Jerrys to randomly grow fingers off their hands. Plus, they were able to easily transition between Terry's multiple forms using just a few controls, pivotal in scenes where Terry mutates into objects on Earth, like this handrail, or this bag of chips. But of course, even something so new and unusual couldn't have been made without looking to Pixar's past. The stretchy software that built Hank and Dante's tongue allowed Terry to disguise herself in elaborate ways, like in this heart monitor, and this brick wall. And the counselors couldn't just move the way a person could, posing another major challenge.

Royce Wesley: Since they don't have legs, right, They just slide around on the ground. The closest analogy is actually "Cars" and that kind of stuff.

Narrator: That meant they needed to borrow from the same ground-locking technology pioneered in "Cars" to keep the counselors in motion. When you get so good at making things move realistically, it's OK to sometimes let your imagination run wild.

Royce Wesley: We're not trying to make things look necessarily perfectly real. What we're trying to do is make sure that the emotions that are coming out of the characters, and what they're thinking, feel 100% real.