Lucy – Paris Car Chase VFX

by Graham Edwards

Lucy - Cinefex VFX Q&A

What would you do if your brain power was suddenly increased by a factor of ten? That’s the premise of Lucy, the new film from Luc Besson, in which Scarlett Johansson plays a drug mule who receives an unexpected dose of her illegal pharmaceutical cargo … and develops superhuman powers as a result.

While the main visual effects vendor for Lucy was Industrial Light & Magic, 164 VFX shots were create by Rodeo FX. Of these, 73 shots feature in a high-octane car chase sequence through the streets of Paris. Rodeo’s contribution to the film represents about eight months’ work for a crew of around 60 artists, plus a management and support team of 15.

In this behind-the-scenes Q&A, François Dumoulin, Visual Effects Supervisor at Rodeo FX, details the planning and execution of the visual effects used to enhance the stunt-filled live-action shoot.

"Lucy" police crash with visual effects by Rodeo FX

How did you get involved with the show?

Rodeo FX had recently completed a car chase sequence with VFX Supervisor Nick Brooks on Now You See Me. Nick was very pleased with the results, and so, when he took on the role of VFX Supervisor on Lucy, he got us on board. I’d also previously worked with Lucy VFX Producer Sophie Leclerc, having been teamed with her as Production Supervisor on Upside Down.

What was your overall contribution to Lucy?

Rodeo FX was initially awarded just the car chase scenes, but we ended up doing a lot more: digital matte-paintings and set extensions, CG props, motion graphics, CG “X-ray vision” and some very complex wire removal.

Did Luc Besson give you a specific artistic direction to follow?

Luc Besson originally referred us to a scene from The Blues Brothers, in which dozens of police cars pile up in a crazy, yet realistic way. For the crushable models of the cars, we compiled our own set of reference material, and studied hours of crash test footage, analysing how the individual components would break, how much debris was spreading out and so on.

For generic animations, rigging studies and suspension behaviours, we were given some great video of the stunt driver rehearsals for the film. We also analysed footage from Paris traffic survey cameras to get a sense of the makes of vehicles, textures and variations of car paint you find specifically in the city. We knew from the start that our asset library of New York taxis and Hummers from Now You See Me couldn’t be used on this show!

Can you describe the car chase sequence?

A police officer is driving Lucy through the streets of Paris. She begins to visualise the data emitted by every mobile device in the environment, and uses it to spot the location of the person she’s looking for. She then gets in the driver’s seat and begins racing through the rush hour traffic. Completely fearless, she drives against the flow through the iconic surroundings of the Louvre, takes a shortcut through a pedestrian arcade, exits in the middle of a crossroads and speeds through a tunnel packed with incoming cars … the whole time leaving crashes and chaos in her wake. We have created lots of really cool shots for Lucy, but the car sequence is something we are really proud of.

How much preparation did you have to do for the car chase?

We started off by doing a very precise previz, based on storyboards from the production. Luc Besson also had this great idea of capturing the major crashes on video using miniature cars – he moved the toys himself over his desk!

Production also provided us with maps of all the locations, with clear indications of where the real and virtual car crashes would happen.

Extracting data from Google Maps, we created a previz that was accurate down to a decimeter. Our lead previz artist, Alexandre Ménard, created hundreds of shots, including all the technical specifications required for the shoot: distance, speed, focal length and so on. We sent each individual take at full length to EuropaCorp. Luc’s editor then cut the previz himself, so most of the sequence was pretty much locked weeks before cameras started to roll.

"Lucy" police car crash - VFX breakdown by Rodeo FX

The complex car chase sequence in “Lucy” called for meticulous planning. Based on production storyboards, tabletop choreography and stunt rehearsals, Rodeo FX created hundreds of previz shots, with precise staging which carried through to the production shoot and subsequent CG prop and collision enhancements.

How extensively did you research the Paris locations?

I flew to Paris with Robert Bock (Rodeo’s VFX DP) to meet the crew while they were prepping for the live-action sequences. Nick Brooks had set up a photo-survey session of the cars being used by the production, which we used as a starting point for our modelling. I also gathered additional reference pictures, such as props that would eventually be reconstructed in CG. My adventures included one very long and lonely drive to a showroom lost in the middle of nowhere, where they sell one particular type of bollard you will see in only a couple of shots!

Just before shooting began, we took part in the tech-scout: a wonderful summer’s day strolling the streets of Paris with Luc Besson and all the heads of departments. After that, I met with the great people of 4DMax, who were in charge of the LIDAR scans. I asked them to collect very precise data, especially all the little details of the road surfaces. Centuries-old pavements in Paris make for a very uneven ground plane, and I wanted to make sure we could produce realistic and accurate suspension behaviours for our CG cars.

The scope of the scanning work was tremendous. We had to cover every inch of pavement from Place de la Concorde to the Louvre – as well as other locations – but the 4DMax gang did it all within the shooting schedule, scanning the locations at night after wrap.

"Lucy" car chase - VFX before and after

Accurate LIDAR scans of the Paris street environments, together with HDRI location photography, helped lock the additional CG vehicles to the original live action plates (Top: live action plate. Bottom: final composite shot)

How did you use the LIDAR data?

We based so much of our work on the LIDAR scans, from the simulation rig we used to get the suspension of the cars right, to the rock-solid match-moving of some extremely challenging shots. We reprojected HDRI and textures on to the LIDAR geometry to generate lighting and reflections. The data was really invaluable.

Was the location shoot exciting, with all that stuntwork?

During the shoot itself, I spent most of my time with Nick and Luc discussing the shots: what could be enhanced in post; where the CG cars would be; how we could make the shot even more amazing. Watching the live-action stunts performed by Michel Julienne and his team was quite something. We would often hold our breath at the end of a take, anxious to make sure nobody got hurt. Those guys are crazy, and their skills are unreal. They created amazing performances, which gave us inspirational plates for our VFX work.

While the real cars were flying around, Robert Bock was running across the set gathering HDRI 360° stills for almost every single take, and from every position. Since the show was being shot entirely digital, we were able later to determine the time of day from camera metadata, and make sure we used the appropriate HDRIs for our lighting. This proved to be critical, because lighting conditions changed a lot from one shot to the next, from early morning bright sun to overcast afternoon.

Luc Besson likes to have things moving fast, so he started editing right away during the shoot. The car chase was the very first scene that was shot, and we got plates turned over and a rough version of the cut just a few weeks after I left the set. From there we jumped straight into match move, layout and blocking of the animation.

You added CG cars to the live-action plates, and also created a number of crashes. How did you go about integrating your work with the original photography?

Nick Brooks gave us initial turnover notes as to where they wanted the extra cars, and the timing of the different crashes. But, really, he gave us enormous creative freedom. We went on adding a lot more cars then initially planned, and a lot closer to camera, too! So the lighting became really critical.

Watch a video breakdown of the car chase:

Under the supervision of CG Supervisor Mikael Damant-Sirois, our team of lighters pulled the relevant HDRI spheres and projected onto the LIDAR geometry. Since both the cars and the camera are moving at high speed, we used lots of different HDRIs in any given shot to get the lighting and the reflections right. On a few occasions where the lighting scenario evolved drastically throughout the shot – inside the tunnel, for example – the HDRI was not precise enough and we had to place light sources manually inside the CG space.

Once the blocking of the animation was approved, and individual car models chosen, we ran a simulation of the suspension rig over the ground geometry. This gave us spot-on ground contact, and kept all the little bumps consistent with each car’s individual weight and scale.

For the collisions and crashes, we developed a rig that deformed the vehicle meshes depending on impact point, speed and angle. Once we got the basic impact right, we would refine it by adding details: modeling specific interior parts that would be revealed, breaking custom parts, and adding secondary animations. On top of that, we ran FX simulations in Houdini for debris, dust and smoke. All these elements were pre-comped by the lighters before being handed to compositors.

Arnold position passes allowed artists to pick specific parts of each individual object in the scene and attach 2D elements to them, change reflections, add dirt or modify the car paint. To supplement the CG elements, we organised a shoot in our in-house studio. We captured live-action debris and smoke, plus a few extras including myself and most of the compositing artists!

Watch a video breakdown of one of the car crashes:

How do you feel when you look back at your experience on Lucy?

This show reminded us how useful on-set elements, references and data are. It was a real privilege to be on set for the scouting, prep and shoot of the car chase sequence, and to have time to take lots of reference picture and HDRIs. And those LIDAR scans were invaluable. It all came in incredibly useful when the time came to light our CG cars and integrate them seamlessly in the environment.

I truly believe that what makes for a totally imperceptible comp is the quality and availability of the reference material. When you’re working on photoreal shots, you just can’t beat reality!

We love it when the audience doesn’t realise that some of the images that they see are filled with CG elements, take place in full CG environments or involve major set extensions. At the same time, it is a challenge to do more conceptual shots – like the mobile rays and the X-ray vision – and perhaps establish a new artistic look: something that has never been seen before and which might become a reference for future movies.

“Lucy” images copyright © 2014 by Universal Pictures. Thanks to Anouk Deveault.