Avengers: Age of Ultron: Trixter reveals tricks of the trade

Avengers: Age of Ultron is yet another visual effects feast! Featuring some of the most complex VFX work seen on the big screen, Trixter talks about the challenges

Avengers: Age of Ultron is yet another visual effects feast! Featuring some of the most complex VFX work seen on the big screen, Trixter talks about the challenges

Avengers: Age of Ultron [2015] was amazing because it was by far the biggest thing weve ever done in terms of scale and complexity, says Trixter Visual Effects Supervisor Alessandro Cioffi. On Iron Man 3 [2013] we did over 100 shots and were focused specifically on different variations of the Iron Man asset, like flying parts and assembling them. For this one, we reached 300 in terms of number of shots and did 7 main assets, dozens of digital props, and different types of effects.

The German VFX company with facilities in Munich, Berlin, and Los Angeles was tasked with establishing the looks of the Pietro Speed Effects and Wandas Magic, as well as sequences involving the Iron Legion and Ultron Mark 1.

Depending on the shot and sequence Pietro [Aaron Taylor-Johnson] was shot at 70 or 120 frames per second with an ALEXA, remarks Alessandro Cioffi who combined the long sequence of frames from high-speed photography with CG effects to create a dynamic silvery trail that is emitted from Pietro while he is running.

Sub frames were used to mix the optical trails so that they gave a nice smeary effect as well as to blend into the CG trails, explains Trixter Compositing Supervisor Dominik Zimmerle. We encountered some staggering so we would had retime the slow motion again with motion interpolation and squeeze them together to get a nice and smooth trail. Sometimes there were tracking cameras which meant that we had to interpolate the frames and the camera movement. This involved a lot of masking, rotoscoping, keying, or relying on the rotomation that we received from 3D to get a nice matte for Pietro. We took him out of the plate, retouched the original Pietro, brought in the smeary trails, and put Pietro on top again so we could get a nice end result.

For us everything was straightforward, remarks Trixter CG Supervisor Adrian Corsei. We did rotomation of Pietro on the plate with the right frames per second and based on this in Houdini we generated particles or volumes depending on the case of his motions. Sometimes we were doing it 120 frames per second, which was overkill for our data, and sometimes it was going smooth. A template was produced to handle the 120 per frames per footage so to assist with the simulation process. We were provided with lighting from a HDRI," Adrian continues. "It helped that the light could be adjusted in compositing as needed.

A motion-control camera was also employed with scenes involving the speedster who also goes by the name Quicksilver. Once the background was taken at a normal speed, the camera motion was slowed down and Pietro could do his action, explains Alessandro Cioffi. It was sped up in compositing so that we could recreate the effect. In general, the factor of speed was 20-times as fast as reality.

Fleet-footed Pietro has a mind-controlling twin sister Wanda (Elizabeth Oslen) otherwise known as the Scarlet Witch. There are subtle details that connect the two visually, observes Alessandro Cioffi. Pietro is mostly silver and blue, so its a cold effect, whereas Wandas was scarlet red which is a saturated effect. The man behind the camera sought to pay tribute to comic book origins of Wanda. Joss Whedon [Much Ado About Nothing] wanted to have something cinematic and dynamic but at the same time he didnt want to go too far from the comic. There was a long period of research, especially on the client side, as to what exactly we could bring into the movie in order for everybody to recognize this character, but at the same time bring something that could live in the movie.

Chris Townsend [Marvel VFX Supervisor] didnt want it to look like smoke or fire or a specific thing that we know, remarks Alessandro Cioffi. Sometimes we would have to push in another direction so it didnt look too much like smoke, flames or water. Whether the Wanda Effect was added into a shot depended on the cinematic situation. Its a storytelling element," Alessandro explains. "Some moments Wanda is not in full control of her power, sometimes she is desperate, and other occasions Wanda wants to mind-control someone. Every moment and action had a different level of intensity in the effect. Wanda can be destructive but also extremely charming and subtle in her influence on the other characters.

Elizabeth Olsen [Oldboy] trained a lot on how to perform Wanda, remarks Alessandro Cioffi. When Wanda does mind-control she has an interesting movement with her fingers. We had to rotomate them. Wanda emits some magic from her fingers to intrude into minds of people. We took advantage of her performance to use the effects as an extension of her fingers. Wanda dictated the pace and subtly of the effect. The mind-control effect has to migrate from her fingers into the head of an Avenger. In some cases an obvious way and in other cases a more subtle way. Our effects were used in compositing to recreate not only directive light on all parts of the body but also some energy that penetrates under the skin, thereby creating a subsurface scattering type of lighting. There was no issue with the red bleeding. The effect does not have sharp edges or a structured geometry. Its smooth and ethereal.

It was always trying to find a balance on how visible the effect should be and avoiding natural comparisons to things were used to seeing, notes Dominik Zimmerle. The red in the shot was a delicate thing. How to fit it into the scene? How red you can go? How broken can it be? The elements we were provided with were good. We used them to create the superficial effects [that come out and off her hand] but we also tried to use them to get some energy flowing under her skin. We see a subsurface effect which crawls from her arm to her wrist to the victim. We had a lot of work to do in compositing to make this whole thing work. We could add additional noise in compositing to distort stuff, and with mattes we could project or map onto the geometry. It was interwoven project between compositing and 3D.

Adrian Corsei and his team of CG artists assisted the compositors in the quest to discover the right look. He explains: When we discovered the effect we were working on a generic color to evaluate its shape and motion. Together with Dominik and the Compositing Department we adjusted the effect shot by shot and ended up the right result.

Ultron Mark 1 only exists in a scene taking place in Avengers Headquarters, explains Alessandro Cioffi. Ultron self-assembles by taking parts of broken Legionnaires and old robots in Tony Starks [Robert Downey Jr.] lab. He continues: At one point one of the rioters in Sokovia throws a bottle of acid onto an Iron Legionaire and we created interesting schematics of a melting and corroding metallic face. Ultron Mark 1 picks it for his own face.

Aided by original artwork provided by Marvel, which established the desired mood, the Art Department at Trixter developed the concept for the character. It went from being a digital sculpture to a proper model and asset once we reached an acceptable form. The simplistic rig was delivered to The Imaginarium, Andy Serkis [Dawn of the Planet of the Apes] motion-capture studio, where James Spader [Secretary] had to perform and interpret his character. Animation Supervisor Simone Kraus helped the guys at The Imaginarium with restraining James Spaders limbs and joints in order to give him the opportunity to physically become Ultron Mark 1. The motion-capture data was delivered to us and we started working on the animation. Meanwhile, Adrian and his crew were building the assets so to give a photo-realistic look to every element of his body.

Lots of research was conducted for Ultron Mark 1. We looked at how old engines get oily and greasy, and how the oil spurts out of broken valves, states Alessandro Cioffi. We tried not only to have a character that could be interesting for the performance but also extremely credible. The sequence evolved beyond the motion-capture stage. When they were editing the movie afterwards not all of the scenes were covered," Alessandro continues. "We had to refer to James Spaders body language and performance in order to recreate bits and pieces, or shots that they were missing. We added fine details as well as complex animation, rigging, and shading so that the character looked like a patchwork of different parts. The idea is that Ultron is a work in progress.

A theatrical approach was taken with the lighting of Ultron Mark 1 so to make him appear scary. We had a spotlight that was above him creating a Shakespearean atmosphere, reveals Adrian Corsei. Its quite a complex character CG-wise. Beside the motion-capture data, Ultron Mark 1 has a cloth simulation because he is full of cables that are hanging around which required a special treatment for each shot. On top of this we have some fluid simulation for the
squirting oil.

The Legionnaires were meant to be drones and robotic in their actions, notes Alessandro Cioffi. They dont act from their own will but are controlled by Jarvis in the first part of the movie and then by Ultron during the fight at the Avengers headquarters. The peacekeeping force created by Tony Stark required key-frame animation. The Legionnaires were more challenging than Ultron Mark 1, states Adrian Corsei. With Ultron Mark 1 we had the James Spader interpretation so we had an idea of what was expected. The Legionnaires had the motion of a human being because theyre bipeds but needed to be robotic. It was challenging to achieve all of the shoulders and pelvises moving and acting mechanical natural. 20 variations of Iron Legionnaires needed to be produced. They start in pristine shape at the beginning of the Riot Sequence and end up quite destroyed," Adrian continues. "For each one of them we had developed several degrees of damage. As we advanced in the sequence we increased the level. We succeeded with a lot of work.

Some compositing demands were to get the lighting nice and theatrical for Ultron Mark 1 but [to not] overdo it, reveals Dominik Zimmerle. The blue light was challenging because we wanted to make it glow, but on the other hand we didnt want it to be unrealistic. We had some demanding scenes where the Legionnaires interacted with the actors so this involved a lot more work than when they are flying through the air. We had to matte-out the stunt doubles. We were supported with shadow passes so that we had a naturalistic light casting from the actors to the CG Legionnaires. In addition, in compositing we tried to help out with creating our own shadows and doing time tweaks on the mattes here and there, so we had a good feeling that the actors and Legionnaires are really are attacking each other. The Legionnaires move differently from the stunt double. We had to remove a lot of limbs so it was a lot of patchwork, tracking, and painting by hand. We used a lot of different techniques there to get a clean surface in order to bring in the Legionnaires.

It was an insanity of frames which starts with a full CG environment and CG characters which are the Legionnaires flying back to New York City

The biggest challenge was a one-minute shot that we worked on, states Alessandro Cioffi. It was an insanity of frames which starts with a full CG environment and CG characters which are the Legionnaires flying back to New York City, up to the digital asset of the Avengers Tower, they go through a digital scanning chamber for checking in, and then the CG camera blends with the live-action camera which goes through to this immense set. Having an in-house Art Department allows Trixter to quickly discover the cinematic vision of clients such as Marvel. Its a preliminary and necessary step that we always do in order to streamline the creative process.

Avengers: Age of Ultron was a year-long project for Trixter. It was a beautiful team effort as everybody brought their own experience, knowledge, and expertise," Alessandro Cioffi concludes. "Theres CG, compositing, green screen, graphic design, and concepts for digital assets. It has everything thats Trixter today.

All images Copyright: (c) 2015 Marvel Studios

Related links:

Trixter official site
Houdini effects for films
Avengers: Age of Ultron interview with Chris Townsend
Inspiration from the Digital Art Masters

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