Marvel exec vp production Victoria Alonso offered an inside look at how more than 2,000 visual effects shots were created for each film.

Director James Gunn himself demonstrated Baby Groot's dance for the visual effects artists who designed the opening sequence in Guardians of the Galaxy: Volume 2. Since multiple effects houses worked on the sequences that featured the raccoon Rocket in the movie, a bible was created so his look would remain consistent. And for Spider-Man: Homecoming, extensive motion capture of actor Tom Holland was employed so his movements would be reflected throughout the film's action sequences.

Those were a few of the secrets behind the two most recent Marvel movies, featured today during the final day of the SIGGRAPH conference in Los Angeles.

Even as Marvel’s 20th film, Ant-Man and the Wasp, was starting production, the visual effects teams behind the studios last two movies appeared before packed houses at two sessions on the making of Spider-Man and Guardians 2.

Moderating both sessions was Marvel Studios executive vp production Victoria Alonso, who earned cheers as she saluted the "hundreds of VFX artists that come from all over the world and make our dreams come true. You are awesome."

Spider-Man and Guardians 2 each had more than 2,000 VFX shots and roughly a dozen VFX vendors. With that staggering challenge, Alonso emphasized that that meant everyone had to be a team player: "The only way to have a project of this size finish on time is to share [assets]. Collaboration is the key," she said.

But the contributors first had to earn their place on the team. For the Spider-Man reboot — the first Spidey film that Columbia produced with Marvel — Alonso admitted that she initially didn’t want to use Sony Pictures Imageworks, which was the lead VFX house on all of the previous Spider-Man movies.

"I told [former Sony Pictures Motion Picture Group head] Amy Pascal that I didn’t want to work with them. I wanted a different look for this film," Alonso explained, adding that she changed her mind when one day she received a "phenomenal test. And then I was told it was Imageworks. I said, 'Yes, we have to use them.'"

Imageworks created most of the third act of the film including the final battle on the beach at Coney Island. "I have been proud and humbled by their work," Alonso said. "[Imageworks VFX supervisor] Theo Bialek and the team knocked it out of the park."

The Spider-Man session included a look at that sequence, as well as the Staten Island Ferry sequence, led by Digital Domain; and the Washington Monument sequence, led by Method.

“[Actor] Tom Holland has a very specific way of performing. We want to keep his essence, so we wanted to use as much motion capture as possible. It was very important that you see every move that he made,” Alonso said, adding that the bigger action sequence also made use of hand-animation.

For Guardians 2, VFX supervisor Christopher Townsend explained that with multiple VFX houses all working on sequences that contained CG characters such as Rocket, “trying to create a single performance was incredibly challenging.” He related that VFX house Framestore created a bible for creating Rocket, which was shared by every VFX house, in order to have a consistent look and performance.

One of those VFX houses was Trixter, which has worked with Marvel before. “But [initially] I didn’t want Trixter to work on Rocket because I didn’t think they had a fur pipeline that was strong enough,” Alonso confessed, before then praising their work, adding, “But they went out and proved they were worthy.” She used such stories to send an encouraging message to the artists in the audience, advising, “Don’t listen when you are told you can’t do something.” VFX houses Method and Weta were also represented on this panel.

A highlight of the Guardians session was the making of the movie's three-minute opening sequence, featuring Baby Groot dancing with mayhem behind him. It involved pre-visualization, live action, CG — and “we shot James Gunn dancing with a few cameras as reference,” Townsend said, showing the clip of Gunn performing the opening dance alongside Baby Groot.

“How much do we love Baby Groot?” Alonso asked to cheers. “Who would want a whole movie about Baby Groot? I’m trying.”