Avengers: Endgame is groundbreaking on many levels, and visual effects supervisor Matt Aitken can tell you all about them.
Aitken, who heads up Weta Digital's visual effects team, is one of many crafters of some of the most iconic CGI characters on screen, including Gollum in Lord of the Rings. Josh Brolin, who plays the Avengers' biggest villain yet in the form of beefy, purple CGI alien Thanos, became the team's next project.
Under tight restraints, minus a full script, Aitken and Weta pulled off an Avengers-level feat. They worked closely alongside brother-director team Anthony and Joe Russo and said goodbye to characters they'd worked with for years.
Venture forth for behind-the-scenes details on how certain elements of Endgame were crafted, and how the technology that went into building Thanos may have changed Marvel for good.
Warning: Spoilers for Avengers: Endgame ahead.
1. Iron Man's suit change
With the world waiting with bated breath for what's set to be the highest-grossing film of all time, you'd expect Endgame to have been fine-tuned and finished well before the premiere date.
That is true -- sort of. "The last shot we finished was less than two weeks before the premiere," Aitken says. It was "that little shot where Tony snaps."
Iron Man, aka Tony Stark, nabs the Infinity Stones from Thanos and uses them to disintegrate him and all his allies. Sadly, the consequence of that is Tony himself dies.
"It's a crucial shot in the film," Aitken says. The shot involved a fine balancing act between showing how the power of the stones fatally damaged Tony, and showing how the suit fought back to protect Tony.
Aitken confirms that the iteration of Tony's armor in Endgame is the Bleeding Edge Armor from the comics that can self-repair, transform and, as Tony exhibits in , patch up wounds with a nanotechnology spray.
"So there's all that going on but at the same time we didn't want it to be so visually distracting that it took the audience's eye from Tony," Aitken says.
"His face is really the important storytelling bit that's going on here."
Marvel visual effects supervisor Dan DeLeeuw reviewed Weta's first pass. The feedback was: "There was just too much going on," Aitken says.
After toning it right down and two or three more goes, they got the power of the moment right. "Every one of those iterations involved going all the way back to our scripting of our complex Bleeding Edge tech simulation," Aitken says.
"It was important and we just kept working on it until the very last minute."
There's another layer of sadness to Tony's death. Aitken and Weta have been there for Iron Man since the forest scene in the first Avengers film in 2012, where Iron Man, Captain America and Thor meet for the first time.
"It's really nice bookending those three heroes of the MCU," Aitken says.
2. The difference between the two big Thanos battles
In Infinity War, Iron Man, Doctor Strange, Spider-Man and the Guardians of the Galaxy battle Thanos on his home planet Titan in a last-ditch effort to prevent him from acquiring all the Infinity Stones. Star-Lord, aka Peter Quill, doesn't follow the plan and consequently Thanos succeeds in his quest -- and uses his new kitted-out Infinity Gauntlet to attack people with actual planets.
In Endgame, a film which throws down the timey-wimey time travel gauntlet, the Thanos we meet in the final end battle is slightly different. For one, he's four years younger.
"He's more agile, more powerful," Aitken says.
He's also wearing armor, whereas on Titan he was dressed right down in what Aitken's team calls his "philosopher outfit" -- "because he's in a more philosophical frame of mind," Aitken says.
On Earth, in one of the biggest crowd-whooping moments of the film, Captain America proves what everyone knew, which is that he's worthy enough to lift Thor's magical hammer, Mjlonir, and uses it to launch a one-on-one attack on Thanos. Yet even with Norse god lightning strikes, Thanos overpowers him.
"Part of the fight where he's just laying into Cap, smashing up Cap's shield, he had to be incredibly flexible and agile," Aitken says.
However, by design the heavy armor worked against that. "Thanos wouldn't have been able to lift his arms above halfway," Aitken says.
So rather than have the armor restrict Thanos' movement, the team tweaked the design to be flexible in places where it doesn't "read" and have him be fully mobile.
"We did some subtle behind-the-scenes work on his armor without destroying the visual effect of the rigidity of the armor," Aitken says.
3. The origin of the women of Marvel scene
Having worked with the Russo brothers on Infinity War, Aitken and Weta developed a level of trust with the filmmakers that extended to one memorable scene in Endgame.
"We're able to do what Dan DeLeeuw refers to as 'plussing the action,'" Aitken says. That includes refining CGI scenes, adding complexity and coming up with suggestions on how the shots can be a little different.
The Russo brothers "won't take all of [the suggestions] on board, but often they do," Aitken says.
"The most significant contribution was around the women of Marvel section."
Every female superhero in the Marvel Cinematic Universe, aside from Black Widow -- who's dead -- band together on the battlefield outside Tony's compound to help Captain Marvel ferry the Infinity Gauntlet into the quantum tunnel in Ant-Man's van.
The run of action that follows involves the heroes taking on the Leviathans and collaborating in various ways before Thanos throws his blade and destroys the quantum tunnel.
"That whole run of action was one that the filmmakers always had two or three ideas of how that could go," Aitken says.
The Russos shot material late last year, but by the following February the sequence still hadn't taken shape. Weta received a call from the Russos saying they wanted the vendor to take it on. Their normal previsualisation company, called Third Floor, had wrapped and moved on to other projects.
"So that was about really getting together and brainstorming action beats and coming up with rough animation," Aitken says.
The team cut together a sequence, sent it off as a proposal -- and received positive feedback. The editor, Jeffrey Ford, did a pass on it -- "tightened it up a little bit" -- and the almost fully CG sequence took form.
4. No script but an Avengers-size team
Not only is Marvel notorious for keeping its script so tightly under wraps the actors have restricted access, behind-the-scenes artists receive the same treatment.
"We would never actually get the script," Aitken says.
What Weta worked with was an "editorial cut": They received essentially a rough cut from Marvel's editorial department, involving green screen elements and sometimes a black card with text describing the action.
Weta took on the majority of CG scenes in the film, totaling nearly 500 shots. To meet their tight, 16-week deadline for the Thanos battle scene, around 1,400 people at Weta "touched the show in one way or another" with a core team of 600 artists.
"You can do a lot of work at a high-quality level in a short space of time," Aitken says.
5. Advancements in Marvel technology
Going forward in the MCU, Weta and the Russos not only fine-tuned their working relationship, but the technology used to create such big bads like Thanos.
"We were always upping our technical approach," Aitken says.
The specific challenges of Marvel's films required the development of new technology. Thanos was one of the most featured digital performers Weta had ever worked with, including Gollum.
One of the new approaches involved using an "actor puppet" for the first time. Instead of just taking the facial performance of Brolin and applying that straight onto a digital Thanos, Weta took on an intermediary stage involving a digital version of Brolin himself. The team developed the facial animation on top of that version and compared it to the live-action Brolin. This let them capture every nuance of his performance, which they migrated onto the digital Thanos.
"We continue to up our game," Aitken says.
For the next phase of the MCU, Marvel will no doubt be searching for ways to top Thanos' big-chinned villainy.
"Ultimately in solving those challenges, we've come up with techniques and approaches that will help us on future films in the MCU and otherwise," Aitken says.