Alita: Battle Angel VFX Breakdown

Weta Digital, DNEG & Framestore  worked on VFX for Alita: Battle Angel. James Cameron produced this movie, Robert Rodriguez  directed this movie, Eric Saindon at Weta Digital lead as VFX Supervisor & Michael Cozens as Animation Supervisor.

DNEG’s main body of work in Alita: Battle Angel was creature (cyborg) animation. This included the ‘Factory Gang’ in the crazy bar fight scene, as well as the cyborg, ‘Amok’ in the Ido flashback scene. DNEG worked on 260 shots.

In addition to creature work, there was quite a bit of environment work completed for the pick-up rollerball game, as well as the addition of all rollerball skates within that same sequence.

Framestore delivered 263 shots for this movie. Framestore’s work on the project encompasses a broad range of VFX; from the floating city of Zalem, to the vast Iron City and the Motorball stadium; featuring keyframe animation of robot-driven team players, cheering crowds and the building of the vast stadium itself.

With Weta Digital creating the character of Alita, this was an example of a seamless and successful collaboration between VFX studios. In the shared shots, renders of Weta’s animated characters would be placed in Framestore’s worked-up environments, complete with special effects and final comp. A portion of the work was also completed in full by the Framestore team, including the creation and animation of the motorball team players, as well as stand-out environments.

Models already developed by Weta Digital for Iron City were ingested into the Framestore pipeline and laid out using the studio’s proprietary layout tools. A huge build out of the city commenced. ‘It was a lot of work and the results reflect the passion and dedication the environments team put into the process,’ says Nigel Denton-Howes, VFX Supervisor. Alita was a very large project for Framestore environment’s team, who collaborated with modelling to build the city made up of nearly 300 assets. Says Jerome Martinez, Environment Supervisor, ‘we worked on the environment for about six months – from ingesting, to build, layout and lighting. At the same time we were working up concepts to show the client what direction we suggest to add polish to the final picture.’

Framestore were thrilled to get the chance to work on the Motorball sequences. Motorball is the most popular spectator sport in the Western District of the Scrapyard, the action set in a vast stadium holding a crowd of 100,000 fans. The team were supplied with a low-res model of the stadium from the pre-vis, which was then built using 321 separate assets. Artists were given details of where the track should be, before lighting the shots around the action.

For the crowd, the team worked up several archetypal characters and randomised a huge variety of clothing to provide variation in the audience. ‘These were then driven by cleaned up motion capture,’ says Denton-Howes, ‘which we captured in-house at Framestore. Each of these was then cached and then those caches were populated throughout the stadium.’  A system was developed to quickly select animation to apply to the individuals alongside, ‘we could then make them sit, stand and even do the Mexican wave,’ adds Martinez.

Framestore created eight keyframe animated ‘Pro’ Motorball players for the sequence where Alita is introduced to the sport. These ‘Pro’ players are cyborgs purpose-built for racing, and the team used reference including motorcycle races to inform the movement and action. ‘Initial concept artwork existed’, says Andy Walker, CG Supervisor, ‘but the assets team had a great opportunity to redesign several aspects and alter the mechanics so they could articulate freely enough to play the sport.  After discovering one team member looked exactly like one of the concepts, we scanned several of the crew to get great reference for the CG faces.’

The action veers from the stadium and into the outside world of the Iron City, where the characters chase Alita through the streets, complete with a burst water pipe and an array of FX integration. Weta provided a fully rendered Alita for the sequence. ‘We treated the Alita material like this was our foreground plate that we could comp into’ explains Sylvain Degrotte, CG Supervisor. ‘After this the environment team went in to replace and look-dev the surroundings.’ Water simulation was created using Houdini, ‘the effects work was nuanced but challenging’ adds Denton-Howes, ‘with every shot having interactive elements both with our characters, but even more impressively with characters provided by Weta.’

Zalem is a floating city which sits above the Iron City; it’s an aspirational, futuristic city with modern curved, sleek buildings. The audience need to see the city in close-up, therefore the environments team had to develop a large portion of the city in CG, using 330 assets and over 5,000 lights, with Digital Matte Painting used for a few wide shots and clean-up. A time-lapse sequence demanded additional interest, including the use of clouds moving across the cityscape.

As Alita was filmed in native stereo, the team reviewed the stereo footage in dailies to track inconsistencies and develop creative CG solutions where simple paint fixes were not an option. ‘Shooting in stereo is still a rarity in Hollywood, so Alita was a great opportunity to dust off the tool set’, says Walker. ‘Although there were massive challenges, there was nothing better than reviewing brand new shots in full stereo glory, finding the sweet spot for dimension and impact versus scale.’

Rising Sun Pictures created breathtaking shots for two key sequences in the film, including a furious battle between soldiers from Earth and fearsome cyborg warriors known as Berserkers.

Weta Digital VFX Supervisor Charlie Tait and VFX Producer Kevin Sherwood, collaborated with Rising Sun Pictures on the moon battle sequence as well as a second, equally complex sequence set inside a translucent satellite used to train cyborg fighters in zero gravity. For the former, RSP produced the lunar environment as well as spacecraft, weaponry and pyrotechnics, and integrated Alita and hero CG characters provided by Weta Digital. Although fully CG, the sequence looks photoreal with the moon environment rendered in precise detail and the action, including explosions and clouds of debris, calibrated to conform to real conditions.

Integrating falling debris with the scene’s dozens of CG characters, all engaged in combat, was a formidable task. “To make the lighting and the swirling dust work properly, we created proxies of many characters, using curves and specs provided by Weta,” says Wood. “Our compositors employed every trick in the book.”

Achieving a seamless, believable and exciting sequence required unusually close collaboration between RSP and Weta Digital. The animation and effects underwent continuous refinement from the initial phases of production through final delivery. As a result, assets were in constant need of updating or replacement. “We did a lot of testing in the early stages to ensure the smooth sharing of assets and renders,” recalls 2D Lead Jess Burnheim. “By the time shots arrived in compositing, the pipeline was so well-honed that the process was seamless.”

The training sequence was produced in a similar manner with Weta Digital artists creating the characters and RSP focusing on the spherical, satellite, high-tech props and atmospheric effects. “Weta supplied a model of the training facility as well as the camera data,” says Wood. “We took their setups, developed their assets and integrated Alita and her instructor who are training with swords.”

In this instance, the team had to simulate zero gravity, making characters and props appear to float freely in the translucent globes. “The weightless effect was keyed off of the animation and hair simulations from character work at Weta,” says Burnheim. “We enhanced it by creating an environment that is clean and clinical, with subtle light flares adding realism. We gathered reference material of other zero-gravity environments and studied how light reacts to edges and strands of hair, how it makes highlights bloom.”

Again, there was considerable back-and-forth between the two facilities. “We maintained a shared schedule and shared targets,” notes VFX Producer Arwen Munro who joined RSP from Weta Digital last year. “That allowed both sides to track progress as we moved forward from work-in-progress and temp phases. The key was keeping lines of communication open and transparency in scheduling and targets. It went smoothly and we are very proud of the resulting images.”

With sharing shots becoming increasingly in common, it’s important that facilities know how to align their pipelines and work cooperatively toward a common goal. “Working with Weta was a very positive experience from the start,” notes Wood. “There was a lot of commentary and things that needed to be changed right up to the last minute, but it was a very smooth run. We had a great time.”

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