Avengers: Endgame VFX Supervisor Matt Aitken on Massive Cinematic Battles, Explosive Power Sets, and More

The longest film in the Marvel Cinematic Universe, Avengers: Endgame was nothing short of a visual spectacle. Throughout its three hours, the film takes moviegoers into alternate dimensions, past timelines, and the depths of a massive battle that included nearly every character in the Marvel Cinematic Universe. We sat down with Weta Digital visual effects supervisor Matt Aitken to chat all things Endgame.

Here's what Aitken had to say about his time on Avengers: Endgame, including the massive, action-packed third-act battle.

ComicBook.com: How early in the process were you able to read the script to this movie? I should probably ask first, were you able to read the full script for the movie?

Matt Aitken: I read a very early draft, which ended up being quite different from the final film. Way back when the project was just kicking off, which would've been like July 2016, I got to read a rough, early draft. That was because everybody approached these two films, Infinity War and Endgame, as kind of one overall project. When I knew that we were going to be involved, prior to Infinity War starting production, I met with the team at Marvel and got to read drafts of both films at that time.

But then I didn't get to read a script again until after we had finished filming, and I got to see a rough cut of Endgame, which ended up being pretty close to the final version of the film.

So this is the fifth film you have worked on with Marvel. It's been said Infinity War and Endgame filmed back to back. Is that something that carried over into your workflow? Was there a break between the two projects for you and the team?

It certainly quieted down a little, but we never really stopped working on this project. We used the time between delivering Infinity War and getting sucked into Endgame to just kind of continue to develop our character work, particularly Thanos. We did a little bit more development work on Thanos in that intervening time, and just got prepped and ready for Endgame.

The thing about Endgame was that they did this big shoot in 2017, where they essentially shot the material for both films back to back, right through 2017 from January to December. They didn't really shoot out the third-act battle, the final end of Endgame, which is actually the sequence that Weta Digital ended up delivering.

They were still thinking about how they wanted to shape that. They were still doing some writing around that sequence, and so they scheduled a period of additional photography, which ran for a five-week block in September and October of 2018. That was almost exclusively shooting the footage for the end battle, and that was what really gave shape to the end battle. They were able to take that footage and take it through a post-viz process and kind of make sure that they had that whole sequence pre-visualized. Then the editors turned that over to us, and that became our blueprint for the work that we did on Endgame.

Now, you did mention Thanos. He's the antagonist in both movies, but then Endgame saw a new version, and it almost seemed like a whole new character. Obviously, he's from a different timeline. How did you and the team manage to differentiate between the two, especially with two productions that were so close together? Did you treat them as separate characters?

You're absolutely right. He is like a slightly different character, but we did use the same base assets for both films. We spent a lot of time, obviously, on Infinity War working Thanos up, but then the Thanos that we see in Endgame is a younger Thanos. He's come forward from 2014, so he's technically like four years younger than the Thanos of Infinity War.

He's more agile. He's kind of at the peak of his physical prowess, and he's also clothed differently. He's wearing the armor. He's in battle mode. We did the sequences on Titan for Infinity War where he was kind of dressed much more casually, and he's more philosophical in those.

We had that work to do to redress him in the armor. We wanted to reflect his youth and his power, mainly through animation ,and that's not so much a change that we make to the base asset, but it is a change that we make to the approach on how we're animating him.

So obviously, we're working off motion capture from Josh Brolin and then the big fight sequences often we're working off motion capture of stunt performers. But at the same time, we need to take that captured motion and extend it through keyframe animation to really find Thanos in the performance. The thing with Thanos is that he's eight feet tall. He's massive. He's incredibly powerful. So there had to be a process of us layering Thanos on top of the motion that we did, off of our motion capture from these more human-scaled performers. That's what we call finding the body mechanic and the motion capture performance and that's a keyframe animation process.

There's definitely that aspect of it, we dial Thanos into the motion-capture performance, we're finding this new Thanos through that process. But there were also some technical changes we made to how he was set up, which was really not so much about making him a different Thanos, but just improving the Thanos that we had used from Infinity War.

As we were working up the shots for Infinity War, we were identifying areas that if we had had time, we would've made these changes to just make him a little bit more sophisticated in the way that we were approaching him. We didn't have time while we were working up the shots for Infinity War, but we took the time between the shows to do some work on the range of facial performance that we could get out of him, particularly around the corners of his mouth.

We found that there was some more complexity that we could add to his rig there to get more nuances of performance and we also did some work adding subtle detail to his overall facial performance to make it more complex and natural, and hopefully as a result more believable.

This wasn't your first rodeo with Iron Man. Here, we see the physical layers forming with that nanotech suit, right? What went into developing this new, cutting-edge suit compared to the work you did on Iron Man 3?

Yeah. That's true. As a facility, we go all the way back to Avengers with Iron Man, so we've done a lot of Iron Man suits. Iron Man 3, there's a huge range of different suits that we developed for that one. But here, in Infinity War, and then subsequently in Endgame, he's got the Bleeding Edge nanotech that he's developed. We worked that up for Infinity War originally, and that's about this idea that the suit is actually made up of these nanoparticles that can kind of form a fluid and move around on the surface of the suit, and reform different weapons, and then kind of solidify and crystallize into a rigid, metal suit.

We developed that tech for Infinity War, and then really extended it for Endgame for two particular sequences. There's the fight with Thanos towards the start of the third act, where he's generating a device we called the Lightning Refocuser, something that is able to capture Thor's lightning energy and then convert it into like a super blast of Iron Man repulsor energy, which he uses to attack Thanos. That was nanotech, and we got to contribute to the design of that particular manifestation of the suit's tech.

But the really big pieces of nanotech action in this film is towards the end of the battle in the Tony snap moment, where Tony realizes that he's going to have to sacrifice himself for the universe. He uses the nanotech aspect of the suit to steal the stones right off Thanos' gauntlet without Thanos even realizing it. So we see the nanoparticles moving the stones into place on Tony's suit and actually forming a version of an Infinity Gauntlet. Then, of course, that releases all the terrible power and energy of the stones, which I think Tony has already realized that, ultimately, this is going to be fatal.

But the suit's trying to protect Tony from this energy, and it's sort of trying to repulse the energy back, but the energy's too strong, and so the suit's getting damaged. We worked up quite a complex simulation where we see the energy surging through the suit, and then the suit's repulsing it back, and these big gouges being gouged out of the suit. We showed a version of that to the studio and they said it was doing all the right things, but there was just too much going on.

They felt that the audience would be watching that and not really looking at Tony's face at this key moment, so there was a process for us and really doing two or three more versions where we balance out the effect of the stones on the suit, and on Tony as well. We're seeing the energy start to flow into Tony's neck and face there also. It was definitely a balancing act because we had to realize that what was going on here was ultimately going to prove to be fatal to Tony. It couldn't just look like he was able to brush this off, and we'd already seen the effect of the stones on Thanos and on the Hulk in the movie. There had to be enough of it, but not so much that it detracted from Tony's performance.

Those were actually the last shots that we delivered for Endgame. And I think they might be the last visual effects shots to deliver for the whole film.

Scarlet Witch has a pretty prominent role. So far, we hadn't really gotten a good or an extended look at her skill set until Endgame, where it's quite massive. How much direction on the use of her powers were you given? Did you have concept art to pull it from or did you have free reign to do what you wanted there?

Yeah, that was great. We certainly get to see her use her powers to the fullest extent here. And I think the way it was explained to us is that every time we see Scarlet Witch in an MCU film, she's developed her power more. She's understanding it more and she's able to use it to an even greater effect. That really comes to a head in the end battle in Endgame where she's really kind of deadly to Thanos. She's able to really take control.

For her, it's only five minutes into the end of Infinity War where she saw Thanos kill Vision, the love of her life, so she's devastated by that, and she's really angry. We got reference from Marvel, particularly from Dan DeLeeuw, the client-side visual effects supervisor. That was primarily frames from the comic book, so there's a lot of great graphic representations of Scarlet Witch's power energy in the comic book. We got some keyframes of that sent through to us, which actually gave us an idea of the overall shape and scope of this effect. But, obviously, we needed to then take that and make it work in a live-action, feature film context. It couldn't feel too graphic and too cartoony. It had to feel grounded in reality and it needed to have a physical presence to work within this live-action context.

That was quite a process for us, to develop the finer details of what this effect would look like. Always keeping in mind that, while it was definitely way more amped up than we'd previously seen it, it still had to be recognizably the same kind of magic power that we'd seen from Scarlet Witch in previous films so the audience is able to identify they know what's going on here. It's not like there's any risk that we are making them think that this is some new energy or some new power that she's developed. It needs to be recognizable as the same powers that she's had before.

In terms of how we realized that, it's really just about getting them and doing the detail work with our effects simulation team. They get them and run particle simulations and body metric simulations, and we render those to a higher resolution. Then those different layers go to our compositing artists and they really balance everything out and find the final look out of those elements. That all takes time, but it's through that process of multiple iterations and reviewing that work as it's developed with the filmmakers at Marvel that we were able to settle on a final look for those sequences.

Another character that had an integral part in this third act is Captain Marvel. It's been said Brie had actually filmed her Endgame scenes before her solo film, right? So how did that work kind of with the wonky timelines? Were you provided advanced reference to Captain Marvel's solo shots so you could match up the Endgame effects, or how did that work?

Yeah, I think she did film some material in and around the same time that she was filming her own film. She was also present for that block of additional photography in September, October, which was I think after she had finished the main shoot for her own film, so the two really just dovetailed together. But certainly, we were sent works in progress of shots from the Captain Marvel movie so that we could see how that team were developing, particularly the look of her binary effect. We needed to make sure that she was recognizable with that. We came up with our own version of that because we needed to make it work in-house with our own software and pipeline, but we were getting very spoiler-ific shots as her show was being developed, so we that we got to see a way to go with her.

Then she was filmed with her physical costume with a great costume from the costume department, but after her sequences were filmed, it was decided by the filmmakers that her costume needed to be more different from the costume that she was wearing in the 25 years ago, whatever the era of the Captain Marvel movie, so we ended up replacing her costume with a CG suit for all her shots.

And then you and the team are tasked with this final battle, right? I mean this is the biggest fight that we've seen in the MCU, so what was your initial reaction? Was it just business as usual when you found out you'd have to combine all of these different characters on screen at once?

No, it was quite a daunting prospect actually. I mean, it's kind of what we're in this game to do. We relish the challenge and we love these opportunities, but still, this is, as you said, the largest battle that's ever been created in any one of these 22 films. The scope was huge. Also, the weight of expectation from the audience on this movie was off the scale, so we knew that we just couldn't muck it up. We had to honor that level of expectation and really honor the fact that this was the culmination of all these individual storylines. But like I said, we relish these challenges and it was really, incredibly satisfying work to be engaged with.

Since the Russo Brothers lifted the quote, unquote spoiler ban, these cast members have been posting all sorts of behind-the-scenes photos. With this final battle, there's a physical set piece involved with this, right? But what ends up on screen is much, much larger. Technically speaking, how large is an asset like this, this virtual set piece, compared to other things you've designed?

Yeah, it had to be quite contained in a way. The idea is that this battle is taking place in the bombed-out ruins of the Avengers compound on the banks of the Hudson River in upstate New York, and so, it couldn't be vast because why would Thanos use his spaceship to destroy unpopulated countryside? So there was kind of a constraint on the size. So if you look at, for example, the environment for Titan in Infinity War, this environment is actually smaller, but that posed its own particular challenges. The key to that was just staging the action within this environment because there's a kind of thread running through the whole battle which is our heroes collaborating and teaming up to get the gauntlet with the stones across the crater, through a bombed out battlefield, across to the other side to where the van with the quantum tunnel is sitting, so they can get the stones back.

Because they would have got there within about the first five minutes of the fight, because the crater is quite small, we had to kind of artfully restage action pieces so that they're covering some ground. Then we back everything up to the other side of the crater and then they cover some more ground and then we back everything up again so they're kind of going over the same piece of crater over and over again, but hopefully people aren't noticing that. We like moving the dressing around and changing the perspective, so it may be that the crater ultimately feels bigger than it is. But we're helping with that by dressing and drifting smoke elements and atmospheric haze and all these things can help make the crater feel bigger than it actually is, so I think it's not something that people have found off-putting or jarring.

And as you said, that actors were filmed on a set. Often what we do is we wrote a scope, we isolate the actors from that set because it needs to look different or maybe the set dressings that they filmed with isn't appropriate for the particular sequence that we're doing, or just because we want to be able to light the environment so that it feels like it's outside and not on a stage. We're replacing a lot of that on-set environment with a hero, CG version, so it's not just the background and the mid-ground that's CG in a lot of these shots, it's the foreground as well.

We look back to Doctor Strange and there's the sling ring effect, something we see only once, twice, or three times if we're lucky. But then coming to Endgame, there's that one shot where we see dozens at the same time. Is that sling ring effect something you had to scale up and redo completely, or is it something that's easily replicated from film to film?

No, that definitely needed some work. We had done the Doctor Strange portals, that sling ring effect that you're talking about, for the fight on Titan. We had shots in the portal sequence in the Endgame battle where, as you said, there's dozens of portals and they're often really huge, there are whole armies marching through these portals. We had to rework our approach to how we generated them. We used the same basic tips, so we're running particle simulations out of Houdini to generate the sparks. We're making sure that the sparks are observing the laws of physics, so they're falling with gravity and they're cooling off in what's a physically correct way, they're dissipating their energy in a physically correct manner so they have a strong grounding in a physical reality.

We wanted to make sure that they were instantly recognizable for people as being the same Doctor Strange sling ring portals from the earlier movies. Because at that really magical moment, when the portals start opening up behind Cap, we wanted people to be instantly aware of what was going on. We didn't want them to be wondering, "Oh what's this strange thing I'm seeing here? Is this heroes arriving or is this more of Thanos' army arriving through some other way?" It had to be very clearly recognizable as these Doctor Strange portals. But yeah, like I say, bigger, more of them, so there was that work involved to make them work in that way.

Then these sling rings are opening up and we see a whole other environment within those sling rings, right? We see Wakanda, we see New Asgard, and various other locations. Were those actually practical shots, or are those something that are completely generated as a part of the portal?

Yeah, all those environments you see inside the portals are entirely CG. As you say there's Wakanda and New Asgard, but there's also Titan and Kamar-Taj and Contraxia, where the Ravagers come from. They had to be CG because we are, essentially, filming those environments with the same camera that we're running on the compound, the battlefield side of the portal. So that as the camera's moving back in these big, dynamic, sweeping camera moves, we want it all to feel like the para lapse is correct and everything's locking together so that there's a connection between what's on this side of the portal and what's inside the portal. The only way that we can get that camera move to be correct is to actually make it a CG environment and then film it with the same camera if you'd like, throughout.

You make it a CG environment and then film it with the same camera if you like, throughout the rendering process. So, they're all entirely built out CG environments with every blade of grass for the battlefields of Wakanda individually modeled. That was great, as well, because that gave us complete control over how we light those environments. It's very important when the first portal opens up that there's a really strong, hazy, kind of flarey light, which is the dawn light in Wakanda and it makes it hard to see exactly what's going on. The timing of that is really important because the filmmakers wanted to really tease out that moment where we realize that it's actually T'Challa and Okoye and Shuri coming out from Wakanda. It couldn't be just two, we had to lose them in this hazy mist and by creating those environments with full CG, that gave us the control to do that.

The sling ring shots lead into hundreds and hundreds and hundreds of soldiers, or thousands of soldiers, right? All lining up, which brings us to Cap's now iconic "Avengers Assemble" line. When you have so many actors on set, were all the actors there or were most of them added in post, or how did that specific shot shake out?

Yeah, no we certainly had shots where we had to combine different film elements because actors just weren't available all at the same time to maybe shoot a certain shot. A good example of that is the Titan portal, when that opens up. Pretty much everybody in that particular shot was shot at a different time just for actor availability. But that one shot that you're referring to there, the "Avengers Assemble" shot, where we push past pretty much everybody, that was amazing. Everybody was there. They got all those people on set on one day and a lot of that footage that the cast shot on that day has leaked online since Marvel lifted the embargo and you can see everybody just having a great time all being together on set that one time. There's, I guess, Iron Man we added later because at one point, he was going to be somewhere lying on the battlefield for that shot. So he's CG'd there. And we obviously, we've got Hulk and Groot and Miek and Iron Patriot is CG, but they were all there. They were all there for that one day, so it was an incredible day on set.

In a previous interview with ComicBook.com, Joe Russo said the one cameo he snuck in at the very last moment was Howard the Duck. Can you tell us a little bit about that process? Was it like "the doomsday clock's at midnight" type of scenario when you added Howard?

I was really pleased to see that he was able to make it in, because if Howard the Duck's in there, then it's kind of like everybody's in there, right? Nobody's missed out. We got that call from Marvel that, we were well underway with those shots, we were kind of close to finishing some of them, so it was a little bit of a scramble. But it wasn't totally last minute. We said he had time to do it, and there was a nice little gap between a couple of the Ravagers that he would just drop right into. It was nice that he wasn't so obviously in the middle of frame that everybody was going to see him straight away. It was a little bit of a nice little Easter egg that people would have to hunt out to a degree.

In the shots, I counted them, he's in there for 18 frames, so I think, in terms of appearances by digital characters that we have made, he may have one of the briefest appearances of any digital character that we've ever produced here. We had to do the whole, you can't skimp on these things, so he's a hero insert, he's got feathers, all the feathers are rigged. He's got hero pictures and he had to be animated. There's no corner-cutting in lots of this work, you just have to do it. We did it all and are just delighted that he could be in there. People started noticing him straight away, I was watching online. It wasn't long before somebody piped up and said, I think it was in response to somebody saying, "Oh, would have been great if Howard the Duck could have been in there!" and somebody piped up and said, "I saw him."

So they've uncovered Howard. Are there more Easter eggs throughout that whole scene that have yet to be found?

No. I could tease it out and say, "I couldn't possibly say," but I think Howard is the big Easter egg and people have seen.

Last but not least, you were involved in the final shot of Tony Stark's life. Was there ever an added sense of pressure?

Oh, absolutely. That as huge. Again, there was a balancing act to achieve there. We had to make sure that his wounds looked severe enough to be fatal, there couldn't be any doubts about that, that's the whole point of his sacrifice. But we had to allow him to keep his dignity through that sequence, that was something that the filmmakers made very clear to us, that they didn't want it to be so over the top gory that it lost its seriousness and it could have turned almost into a farce if you'd gone too far with it. We did several different versions of that. We approached it initially through concept art, and we worked up lots of different levels of damage through concept art and reviewed that with the filmmakers at Marvel. Then we worked that up in CG as a digital prosthetic and that was great because that gave us the opportunity to review the level of damage in the cast and make changes accordingly.

The added pressure on that sequence, of course, was that we had to make sure it stayed completely under wraps. And nothing has ever leaked out of Weta Digital, so it wasn't too terribly concerned about that. But just for people in the facility who weren't necessarily working on that sequence, I didn't want to spoil the ending of the film for them, so we kept that sequence very much under wraps. And it's great to be able to talk about it now, because for the longest time I couldn't talk about it at all.

Just out of curiosity, how do you assign that to a designer? Do you sit down with them and say, "Listen, the movie's about to get spoiled in the most worst of ways?" Did you just kind of draw the shortest straw and they had to get spoiled right away or what?

Yeah, no I think it's surprisingly painful working in this industry it's that you can't, you just have to... I mean there's lots of great shows going on here. We've got Game of Thrones Season Eight and the people who were working on Endgame managed to avoid any spoilers for Game of Thrones and vice versa. But if you're going to work on a show, you just have to expect that it's not going to be the same experience as just going and seeing it as an audience member, fresh for the first time.

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What was your favorite shot in Avengers: Endgame? Let us know your thoughts in the comments below or by hitting me up on Twitter at @AdamBarnhardt!

Avengers: Endgame is now in theaters.