See James Gunn do one final dance as Groot in Guardians of the Galaxy 3

Back in 2015, before writer-director James Gunn was at the center of every superhero universe, he revealed something about Guardians of the Galaxy fans have hung onto ever since: The little dance that baby Groot does in his pot at the end of the movie was modeled on Gunn himself. “I was too embarrassed for anyone to be there,” he told Yahoo, “so I made everyone leave the room and I set up a camera and I videotaped myself dancing. Then I sent the video to the animators and had them animate over that. I begged them not to leak the video!”

Gunn shook off the shame (literally!) for 2017’s Guardians of the Galaxy 2, and he personally posted a video of him originating all of Baby Groot’s dance moves from the movie’s opening musical sequence. And to finish the trilogy off in style, he created the moves for adult Groot in Guardians of the Galaxy Vol. 3. A new video provided exclusively to Polygon by Oscar-winning VFX studio Framestore shows off a lot of what the company did behind the scenes, from animating the elaborate space city of Knowhere to producing versions of Rocket Raccoon at six different ages to laying adult Groot’s heavy tree muscles over Gunn’s dance moves.

Among many other things, the video shows footage of James Gunn’s brother Sean Gunn in a motion-capture suit, playing the on-set version of Rocket and interacting with the mocap-suited cast members who play Rocket’s experimental-animal family in the movie — robot-armed otter Lylla, spider-legged albino rabbit Floor, and wheeled walrus Teefs. But when James Gunn dances as Groot, he doesn’t wear a mocap suit. Why?

Montreal-based Framestore VFX supervisor Stephane Nazé explained to Polygon that Gunn’s performance as Groot isn’t a mocap performance — it’s rotoscoping. He isn’t providing real-time digital data that will be used to animate Groot, just a general visual reference for the character. “While we had James Gunn’s excellent performance and tracked him to provide accurate data, our Groot was entirely hand-animated,” Nazé says. “James brought a tremendous sense of fun and excitement to his performance, and it was down to our animators to capture both the moves and the spirit in order to bring Groot to life.”

Nazé says the big challenge in animating Groot over Gunn came from the “vastly different dimensions and proportions” of the director and the character. “Groot, especially since he’s now in his linebacker phase, is obviously bigger and heavier, so you couldn’t transpose James’ exact performance,” he explains. “We needed to adapt and accommodate for Groot’s weight and proportions, as well as the complex array of organic materials — twigs, vines, bark, and so forth — that make him what he is and allow him to move the way he does.”

Image: Marvel Studios/Framestore

Framestore’s VFX breakdown video also shows something surprising for such a heavily digital environment: an actual golden retriever used as visual reference for Cosmo, Maria Bakalova’s hyper-intelligent talking cosmonaut dog. Framestore tells us that this reference dog is named Slate, and that while most of Guardians of the Galaxy Vol. 3’s animals are purely digital creations (apart from a rabbit and turtle used in a speed-evolution scene, which the London Framestore team drew from footage of real animals), Slate was used as a reference to make Cosmo as real as possible, from facial expressions to details like dust on the fur.

“As soon as you give an animal human traits you risk destroying any sense of realism,” Nazé says in a document breaking down the images in Framestore’s effects reel. “The animation team spent hours and hours researching canine expressions and poses that could equate to human emotions — joy, surprise, curiosity, etc. — so as to stay true to what people know and love about dogs while allowing for a subtle and often humorous performance.”

The many versions of Rocket Raccoon moving side by side to illustrate their differences and similarities is a particularly compelling piece of imagery. London VFX supervisor Alexis Wajsbrot tells Polygon that of all of them, the adolescent version of Rocket was the hardest to get right. “We’d created adult Rocket and worked on him several times before, and with his ‘runt’ incarnation, we worked to match a real [raccoon] kit,” he says. “So while we were building [the runt version] from scratch, it was relatively straightforward creatively — a case of balancing photorealism with that sense of cuteness and play.”

But adolescent Rocket had to represent a recognizable balance between those two stages. “We had to understand what was it that would make him look younger, find the right implants to tell his story, logically explain the move from quadruped to bipedal form, and elements like the creation of his shoulders, thumbs, and knees,” Wajsbrot says. “Animation-wise, the challenge was to make him a bit more animalistic than his adult incarnation, albeit following the same ‘rules.’ We bent him more, and had him emote slightly less.”

Wajsbrot says the animation team’s biggest triumph was redesigning Rocket for Guardians 3 so that adolescent version of the character was “capturing his transitional state of self.” He describes it as a “numinous phase” that was “really subtle and nuanced, hitting a midway point between the more naive and friendly young Rocket and the grizzled, hardened Rocket we all know and love.”

Guardians of the Galaxy Vol. 3 is now streaming on Disney Plus. More of Framestore’s work and behind-the-scenes breakdown can be seen at the company’s website.