Nvizible Takes a Leap for ‘Kingsman: The Secret Service’

The VFX team from Nvizible in London created, animated and composited her legs into 110 of the 230 effects shots their artists completed for the film. The work was complex and interesting because it was almost entirely performance-based, which meant devoting extra time to on-set supervision working with both the film crew and a motion control team. Shots, performances and multiple passes had to be planned carefully, making extensive use of witness cameras.

Performance Plus

Nivizible came on board the production about three months before the shoot, in August 2013, to begin planning their approach, and therefore were confident about what data and images they would need from set. “We contributed quite a lot to the design of the legs and blades, and carried out a series of animation and motion tests to determine what kinds of movements would both look elegant and enhance the shots,” saidNvizible’s VFX supervisor Matt Kasmir.

“The goal was to keep the design simple and sleek. When we received the initial plates of Gazelle, we found a fair amount of animation work was required on the digital prosthetic itself to give it the feminine look we wanted to match and work with Gazelle’s own style and her dance-like performance – light, springy and athletic.”

Shots featuring the fight scenes required her to leap through the air, avoiding gunfire and extending her blades. The actress Sophia Boutella was able to perform many of the dramatic fight moves herself, which was helpful because the director Matthew Vaughan wanted to keep the performances within the realm of believability – extreme and impressive but realistic, not relying on digital doubles for more than a few frames at a time.

Therefore, all action was performed either by the actors themselves or by stunt doubles. No fantasy flying was required, and this applied to the camera work as well. “All camera moves were real, and consequently, giving Gazelle a superhero’s personality did require us to plan the camera angles and positions with care,” Matt said.

High Frame Rates

Because Nvizible was to replace her lower legs in post with a CG prosthetic, they needed to be able to see her feet clearly in every shot, whether she was wearing high heeled shoes or was barefoot. The high action performances made this challenging and therefore they captured every shot with a witness camera so that they would have an alternative view to the hero camera in case a prop or another character obscured their view.

“Adding to our challenge was the fact that Matthew Vaughan’s style favours dramatic retimed shots, which we were familiar with from working on one of his previous projects, ‘Kick Ass 2’,” said Matt. “Nearly every shot was captured at a high frame rate, averaging 120 fps, and retimed in the edit. In a single shot, for example, there may have been as many as 2,000 frames. Even though, by the time the re-timing was complete and the edit was locked off, there may only have been 100 frames remaining, we still needed to track every frame because the cut would change several times.”

The high speed photography required for the slow motion was captured with the production’s ARRI ALEXA XT hero camera for shots up to 120 fps. For those up to 300 fps a RED camera was used, and a Phantom for others up to 600 fps.

Multiple Passes & Motion Control

Matt said, “Some of the shots required multiple passes for various reasons, including safety. When several actors were to appear in the same shot and had to jump over each other, needing a safety rig, it was sometimes better to shoot them separately and combine the shots in post. Stunt actors were used as well and sometimes had to transition to the lead actor within a single shot. For these situations, we planned out the multiple takes precisely and captured them with motion control set-ups, using cameras and a team fromThe Visual Effects Company, also in London.”

In one case, The Visual Effects Company’s High Speed 360 rig was used, which spins through 360° around actors performing on a static platform. A lift column and a special head are a part of the system, so that the camera can rise and fall as well as pan and tilt with focus and zoom during the rotation for more control over the shot. Due to the mechanics and varied inertias involved, the configuration was a bespoke design and had to be adapted to suit the individual shot.

Of the two other rigs employed, the Milo, a portable, stable, agile system that is able to precisely repeat high-speed moves running on various lengths of precision track. It is used with software that allows the manual operation of any axis to be saved and replayed with frame accuracy. The EIGER arm, also used on 'Kingsman', is a custom made crane arm that can be fitted to the Milo rig to increase the operating envelope of the camera but is still precise enough to allow accurate programming of moves.

Roto-animation

Flexibility was key. In one shot, for example, there were as many as four performers to coordinate, and occasionally, the Nvizible’s artists needed to blend a stunt actor to a digital double to the main actor – in a single shot. In such cases, CG doubles were created based on comprehensive body scans, and used as a ‘bridge’ between live action and digital elements. While on set, video overlays were used to monitor how well they would be able to line up these elements in post, when they would use roto-animation to invisibly align and blend the live action with CG.

Pre-vis, which Nvizible created for themselves in this case, was also a critical step to save time and prevent having to repeat too many shots. Sound cues were used to help coordinate the actors as the crew captured the passes. Once one pass had been shot, it would be played back during the shoot of the next pass at the speed it would be used in the film, and a sound cue would be given for the next actor to begin performing.

The team also shot their own clean plates while approximating the same camera moves. Because Gazelle’s metal legs are very thin, Sophia wore green leggings on set with tracking markers, which were keyed out and replaced with the CG elements and the background material. The clean up work around her sometimes had to be projected in 2.5D to accommodate the camera moves. www.nvizible.com