Alita: Battle Angel VFX Breakdown

Weta Digital, Double Negative & 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.

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.

Alita: Battle Angle VFX Breakdown

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.’

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