Behind the VFX: The Trixters of Age of Ultron

The second Avengers movie, Age of Ultron, may be the biggest and most anticipated visual effects flick to launch this year. Certainly it has a lot to live up to with the huge worldwide success of its predecessor. Heading up the VFX department is veteran Chris Townsend, who oversaw a variety of Marvel's contracted vendors like ILM and Double Negative. However, walking among the VFX giants of the industry are houses like the Munich-based Trixter, a smaller studio with a growing reputation for bringing big budget professional effects with a minimal amount resources. In fact, Trixter was responsible for delivering some of the film's most thematically important and technically difficult shots and characters. Recently, we talked with the studio's CG, compositing, and VFX supervisors for their insights into how they worked their digital magic for the film and what software they used to make it happen. (Warning: Article contains spoilers). In all, Trixter worked on 294 shots for key sequences and characters within the Age of Ultron and another 106 for its trailers for a total of 400 shots. Here is a list of their shots, assets and animations:
  • Concept and look development for Ultron Mark I and the Iron Legionnaires.
  • All shots of Mark I and the Iron Legionnaires in the “Party Fight’ sequence (140 shots).
  • Worked on character creation and animation of digital doubles for Quicksilver (+ speed effect FX), Exo Hydra Soldiers, Captain America, Iron Man and FX of Scarlet Witch’s magic power.
  • Various environments and digital assets.
[caption id="" align="alignnone" width="800"]legionnaire_crawl Photo courtesy of ©Walt Disney Studios[/caption]

Party crashers

Trixter produced the VFX for the iconic "Party Fight" sequence, which sees an Avenger cocktail party suddenly interrupted by the story's robotic antagonist, Ultron Mark I. Following Tony Stark's foray into developing an A.I. peacekeeping army of robots called Legionnaires, Ultron Mark I self-assembles and plans to use his robot army to destroy Stark and the Avengers. The Mark I is the first iteration of Ultron Prime, and James Spader's mocap and voice-over performance is being hailed as a standout for the diabolical, bionic nuisance. [caption id="" align="alignnone" width="800"]mark1_bottle Mark I takes a bottle of acid to the dome. Photo courtesy of ©Walt Disney Studios[/caption] Trixter's CG Supervisor, Adrian Corsei explained to us that Marvel initially gave the studio some rough concept images for the Mark I's design. Based on those concepts, Corsei's department of 25 began to sculpt an asset using ZBrush. Next, they imported it into Maya, and a quick rig was constructed and sent to the mocap studio, Imaginarium. There the model was used to help Spader view his performance in real-time. "For the first time, Spader could see himself in what we call the 'digital mirror,' Alessandro Cioffi, Trixter's VFX Supervisor, explains. "His movements and performance were done in real-time, displayed on a monitor so that [Spader] could see the character as he would exist in the movie. He could complete his transformation into Ultron by looking at himself moving as Mark I." [caption id="" align="alignnone" width="800"]mark1_nohead Photo courtesy of ©Walt Disney Studios[/caption] In the scene, Ultron Mark1 is only half assembled. He hasn't yet taken on the form of Ultron Prime, his ultimate iteration, so the film’s key creatives wanted to create a spooky and creepy appearance for him. Getting the right look took a lot of collaboration. Whedon and Townsend were both open to suggestions for Mark1's look, allowing Cioffi and his team to take a big part in the creative process. They approached it from a cinematic perspective adding lighting, modeling, and animation that would underscore Spader's performance. "We tried to think like a DOP," Cioffi explains, "We tried to help [Spader's] performance by providing some additional drama through lighting. The set looked slightly like a stage. The first thought we had was that it looked almost like a theater, so we created a very theatrical light that gave the character a backlight or a slight three-quarter ring light. He's metallic; he takes light from the environment, but there's a very strong key light all the time that gives a shape to his body and defines his evil look. His face is always lit from two sides; these elements created a very strong, diffused feeling to the scene." [caption id="" align="alignnone" width="800"]mark1_1 Mark I's dramatic entrance during the "Party Fight" sequence. Photo courtesy of ©Walt Disney Studios[/caption] Cioffi and company also tried to complete the Mark I character by adding plenty of destructive details and broken effects. "He's an incomplete robot," he explains, "He self-assembled just a few minutes before he enters the 'party fight' scene. He's very unfinished, almost broken. He has cables hanging and oil dripping from his limbs. The Mark I has constructed himself from bits and pieces of broken Legionnaires and old parts of Iron Man suits. He's always asymmetrical in shape, and you can tell he's a weird figure." In collaboration with Trixter's Animation Supervisor Simone Kraus and the team at Imaginarium, Spader's performance was enhanced by the addition of weights and constraints to his body. Cioffi explains the process. "In order to help [Spader] perform," he states, "he had weights attached to one side of his body to create an asymmetrical pose. They also blocked his left elbow to create an arm that was not functioning correctly and weights to one foot, which gave the sense that the robot's joints were malfunctioning." [caption id="" align="alignnone" width="800"]legionnaire_kiss Mark I's apparent loving embrace quickly transforms into decapitation. Photo courtesy of ©Walt Disney Studios[/caption] The resulting mocap data was then returned to Trixter, and a final production rig was created for fine tuning the animation. The Ultron Mark I asset was a quite complex model. Besides the huge amount of geometry, it also had some fabric and fluid simulation. Also, there was the additional animation that was needed to build a convincing looking half-built robot. Cioffi explains, "You need to remember that the mocap data only covers the main motion. We had to add a lot of secondary animation to do for the thousands of bits and pieces of his body that are moving all the time. There were pistons, pieces rotating, thousands little tiny bits that are moving every time he took a step, rotated his head or moved his arm." Despite Spader's inspiring performance and the motion capture, there were instances where Trixter needed to re-work or add animation all together. "Sometimes the mocap data didn't read correctly on the rig," Cioffi states, "so we had to adjust, not so much the performance, but Mark I's poses just to make it more extreme at times. Other times some scenes weren't mocaped at all and we had to replicate the performance in the classic key frame animation method." "There was some incredible compositing," Cioffi continues. "It was very tricky to replace the stunts with our CG assets and integrate them with the actors. The actors were very close to one another, so creating the interaction was quite tricky." [caption id="" align="alignnone" width="800"]legionnaire_factory Photo courtesy of ©Walt Disney Studios[/caption]

The Legionnaires

The studio was also responsible for delivering Ultron's robot army, the Legionnaires. For Corsei and his CG team, one challenge came from simply building the small army, which was composed of 35 props. During one scene the Avengers must take on the army of Legionnaires. Animating such a large army of robotic AI is a task in itself. However, since the Legionnaire army is ultimately defeated by the heroic group, Trixter's team had to build into the fight sequence various levels of damage for the robots' structures. A larger number of variations also meant a larger number of looks from the film's creatives. Cioffi explains, "We had to develop the characters with a variety of modifications and alternatives as there are many of them. Their look was constantly monitored by Chris Townsend, so we had meetings almost every day during the initial stages. Slowly as the production grew, we could tune down the frequency of our contacts to once a week." [caption id="" align="alignnone" width="800"]legionnaire_factory2 Photo courtesy of ©Walt Disney Studios[/caption] Trixter used a wide variety of software on their shots, which included Maya for modeling and animation, MARI for texturing, NUKE for compositing, KATANA for rendering and Houdini for FX. One big change in Trixter's workflow for the Ultron project was its decision to switch to Houdini for its VFX work. Previously, the team had used a combination of 3ds Max along with plugins like FumeFX. The change was prompted by a need for iteration. "This was a big leap forward for us," Corsei states,"If you want to do one shot, 3ds Max is the perfect tool to do it. But if you want to do the same thing over and over again, you need a tool that's able to assetize the effect, to make a template out of it. So we switched to Houdini and the change was quite successful." [caption id="" align="alignnone" width="800"]legionnaire_power Photo courtesy of ©Walt Disney Studios[/caption] Some assets were shared with other studios who were using them in other shots. For collaborating with other vendors, Trixter used the open CG interchange system Alembic. These file exchange systems are becoming more and more effective for studios working together around the world. "Most of the vendors speak the same language," Corsei stated, "Of course, there are small variations between each facility, but the core is the same; the flow is the same. We shared a lot of things like cameras, geometry, textures, and scripts as well. What we can't share now are shaders, which are normally proprietary and developed in-house.

The Scarlet Witch and Quicksilver 

The two newest characters to enter the Avengers universe are Wanda Maximoff and Pietro Maximoff, otherwise known as the Scarlet Witch and Quicksilver. Trixter's animation and VFX department were tasked with handling the superpower FX for both. These included giving form to Pietro's "speed trails" and Wanda's telekinetic and mind control powers. [caption id="" align="alignnone" width="800"]QS_woods Quicksilver's "speed trails" through a snowy forest. Photo courtesy of ©Walt Disney Studios[/caption] Again, Cioffi worked with the film's creatives to get a clear idea of how each character's power should look. "We started off with some concept work. Did some work with Chris on how to prepare the shooting for Quicksilver as he wanted to have a very photographic look for the sense of speed of this character. So we did not only art work for designing the FX, but also for how to prepare the shooting, compositing, and how to break it down into a clear recipe for these two characters" Trixter's compositing supervisor, Dominik Zimmerle, explains the specifics of how these superpowers were created. "Pietro's speed lines or trails were a combination of the photographic trails, which came from the photograph plate, as well as the visual effects trails. Both were blended together. The first step was to get a slow motion plate (120 fps, 72 fps, etc). These depended on the necessities of the shot. They were then blended together with various techniques in NUKE to create the first smoothed trails emitting from Pietro." [caption id="" align="alignnone" width="800"]QS_Hammer Quicksilver does battle with Thor's hammer. Photo courtesy of ©Walt Disney Studios.[/caption] Next, Zimmerle and his team of twenty compositors used Houdini to create FX trails, which they blended with the photographic slow mo plates to have an evenly distributed speed line coming from Pietro. This was also referred to as the "silver trail." The team had to essentially create two different time perspective scenes: one from Pietro's and one from the viewers. During Pietro's time perspective he would appear running at normal speed while everything around him would be sped up many times. Then there were shots where the environment was in slow mo and Pietro would need to appear running at hyper speed. Regardless, the speed lines would still need to exist as Pietro moved. [caption id="" align="alignnone" width="800"]QS_Legionnaires Quicksilver takes out some Legionnaires. Photo courtesy of ©Walt Disney Studios[/caption] This created a challenge for the VFX team who needed to bring two plates together that had been filmed at different speeds. "This proved especially difficult on tracking cameras where no motion control was involved," Zimmerle explains, "It was a little troublesome to track it in so that we could bring everything together, but I think it worked quite nicely" [caption id="" align="alignnone" width="800"]Wanda The Scarlet Witch's mind control aura. Photo courtesy of ©Walt Disney Studios[/caption] The Scarlet Witch's powers of mind control and creating its "aura" also had its challenges. "Visually, her powers were an interesting challenge because they could have both a subtle and profound impact on the plates," Zimmerle explains. "They created a lot of distortion, and you can see it quite easily at some points and others not so much. Wanda's mind control was the result of mixing a lot of elements from Houdini and involving additional interactive light coming from rotos in NUKE."

The one-minute shot

Despite the dramatic depth of the Mark I scene or the shear volume of creation needed for the Legionnaires, the shot most artists at Trixter say they're most proud of was the one minute sequence near the beginning of the movie. The sequence shows five Legionnaires making their way back to the Avenger's HQ (i.e. Stark's Penthouse). Of the sixty seconds, approximately 30 were completely CG, and Trixter was responsible for the animated characters and the interior environments. During the sequence, five Legionnaires fly over NYC and enter the Avenger tower. The camera follows them through an entire CG environment. Then the CG camera marries with a live action camera, going from the lab down stairs up to Tony Stark's studio, before finally settling on a beautiful overview of the interior of the tower with the NYC skyline beyond. "It was an extremely long shot," Cioffi states. "For almost 30 seconds, it was completely CG. It was an entire CG environment, we shared it with ILM, who did the CG background of NYC for us. We were concentrating on the Iron Legionnaire animation and FX and the interiors of the tower. I mention it because it was extremely complex to work on." Trixter was also responsible for producing many other smaller pieces for Age of Ultron. These included modeling a digital double of Captain America, animation for Iron Man, Pietro, Wanda, and Sub Ultron, (an asset from Double Negative) along with some environment generation and winterization.


Trixter VFX Supervisor: Alessandro Cioffi Trixter VFX Producer: Franzisca Puppe Trixter Animation Supervsior/Set Supervisor: Simone Kraus Additional Trixter VFX Supervisors: Adrian Corsei (CG supervisor),  Domminik Zimmerle (compositing supervisor) Software Used:  Nuke, Katana, Houdini, Mari, Maya, Mocha, PRMan, Arnold, Motion Builder, 3d Equalizer, Adobe Photoshop