How to catch a helicopter with a chain (and some fast and furious cars)

Remember that insane multi-car daisy chain and helicopter chase scene towards the end of David Leitch’s Hobbs & Shaw? It’s definitely one of the more fantastical moments in the film, let alone the Fast & Furious franchise.

And, it turns out, it was a scene thought up relatively late in the day, after the crew had already arrived in Hawaii (doubling for Samoa) to shoot what was already an elaborate car and helicopter chase.

“They decided they wanted to up the action another level,” reveals Hobbs & Shaw production visual effects supervisor Dan Glass, from DNEG. “A lot of ideas were thrown around for ways to do that. The winning version was one where the four cars hooked themselves up and get air lifted by the helicopter. They just said, ‘Let’s do it!’, and I’m like, ‘Okay…’”

Right then and there, Glass called up his ‘trusted previs advisor’ Alex Cannon, who was then at The Third Floor and has since joined DNEG to head a previs devision at the VFX studio. “I called him up in LA from Hawaii and said, ‘Alex, I need you to put something together in the next 24 hours.’ And that’s what he did. He pulled together some colleagues and very quickly they hooked up previs for the sequence that’s not far off how it ended up.”

With the previs on hand, Glass worked with stunt co-ordinator Chris O’Hara and special effects supervisor J.D. Schwalm to help realize what became known as the daisy chain scene. It was just part of a stunt, practical effects and visual effects-filled sequence that saw Hobbs (Dwayne Johnson), Shaw (Jason Statham) and friends hook their cars onto a helicopter carrying the cyber terrorist Brixton Lore (Idris Elba), right along the Samoan coastline. The chopper ultimately takes a cliff-side tumble, setting up a fist-fight showdown.

What could be filmed live-action

The live-action stunt driving work was aided by the presence of, of course, several vehicles, drivers and stunt performers, and a real Black Hawk helicopter on location. The chopper provided a large amount of ‘grittiness’ to the scenes, says Glass. “The kind of downwash that comes from a  Black Hawk’s rotor wash is pretty significant, as you can tell with the effect on the dust. And so we tried to get as much of that for real as we could.”

When the lifting part of the sequence takes place, a rig built by Schwalm for the Peterbilt, the truck that Hobbs and Shaw are in, and for the yellow M37 Jeep, enabled the vehicles to be lifted up on their rear wheels. Anytime all four wheels were in the air – and sometimes even when they are not – was when the visual effects team took over (more on that below). A camera helicopter captured the action, which also included some hairy moments dodging pyrotechnics for a few explosive moments in the chase.

Another side to the live-action chase shoot was an extra outdoor bluescreen photography stage in Hawaii for close-ups on the actors. “We built a big wall of blue out in the field and shot in real sunlight and we had rigs again supplied by J.D.,” outlines Glass. “There was one rig that was made up of these vibrating motors under each wheel so the car could get an appearance of driving. And then we had a huge crane which could lift up the back of the truck so that we could film Dwayne and Jason in a vehicle that was actually at an angle.”

After the live-action shoot ended, and while the edit was being crafted, a postvis effort was also underway, overseen by Cannon. “The edit was happening thick and fast and we had an incredible post schedule to put the movie together,” notes Glass. “Once the directors cut delivered, we only had a few weeks, so we had to get a kind of step up, we had to help the edit understand what these things were. Postvis was critical to creatively map out the things that we needed from each visual effects shop, which were DNEG and Framestore.”

‘Let’s go fishing’

The sequence begins with the Peterbilt making a jump, while Hobbs swings a chain that wraps itself around the Black Hawk as it lifts off. “We were able to drive the real truck toward the edge of the jump, but obviously not make it jump,” says Glass. “That was with a stunt double so there was some head replacement work there. We shot the real Black Hawk in position and even kind of moving as if it has been affected as best we could.”

“It’s a CG vehicle for the jump itself, with a digital chain, but a real Black Hawk,” adds Glass. “And Hobbs is actually Dwayne shot bluescreen which we shrunk down into that plate.”

As the scene continues the heroes need more horsepower, so they keep adding vehicles together in the hope of bringing down the Black Hawk; this is the daisy chain moment. Framestore would bring together all the live-action elements, and a host of CG ones, to form the final shots.

“The daisy chain rig allowed us to sequentially connect up the different trucks and easily animate them both as a group and individually,” says Framestore visual effects supervisor Ben Loch. “It gave the motion a natural connectivity as tweaking the position of one truck directly influenced its neighbours. Initially we animated the trucks with lots of violent vibrations and jolts but as we got closer to finalling shots and saw the animation rendered and comp’ed we realized the trucks felt light and too bouncy so we significantly reduced their vibrating. Mostly we referenced other shots in the sequence where we could see the real trucks to get a sense of their physicality.”

As much as possible, the real Black Hawk remained in the plates for the daisy chain and the following scenes. But there were a number of times it was a synthetic version built by Framestore. “We were provided with a digital scan from ClearAngle of the Black Hawk helicopter, this was used in conjunction with a large amount of stills photography to build an accurate CG duplicate that would hold up to some of the demanding close up shots,” states Loch.

“Generally the live action helicopter was always kept as it looked great and you got some amazing kick-up dust and environment interaction in the plate for free. The only time a CG version was used was if the shot involved large explosions then they would leave the Black Hawk grounded for obvious safety reasons and a digital version would be called out. The other scenario was if the plate helicopter didn’t work with the desired action or edit, then it was painted out and a digital version was added along with all the FX interaction.”

Photographic backgrounds

Since the sequence is intended to be a coastline chase, there was also going to be a need to generate background plates. These came from two sources; an extensive photographic reference shoot undertaken by Framestore, and from multi-array camera rigs used during principal photography. These rigs were a Hydra Head mounted on the camera chopper with six HD Red Epic-X Dragons and a vehicle-mounted rig provided by Brownian Motion which consisted of six Alexa Minis, with the images captured incorporated into the final shots. Framestore’s photographic reference shoot in Hawaii took place ahead of the main unit so that they could begin the coastline environmental builds early. Loch details the approach to the reference shoot.

“Jacek Pilarski, one of our environment artists, took the lead on shooting key reference material of the plant life on location, hanging out of helicopters shooting photogrammetry data of the Napoli Coast – all of which was delivered back to Framestore for processing. This recce was only five days which made for a busy shoot, especially with the fact that Kauai is literally on the opposite side of the world from London! That being said, it was incredibly beneficial and really put us in a position to be able to be more flexible with addressing feedback and be able to react to late changes effectively.”

Framestore then built a digital representation of the coastline, approximately two kilometers worth. “All this data was then re-topologized, whereby the quad meshes were generated with clean UVs and corresponding textures from the photography with a de-light process applied,” says Loch. “The next challenge was fitting this coastline geometry to the shoot location terrain which was conveniently on the opposite end of the island so was very different in shape.”

It became apparent early on that it was important from a story point of view that as the sequence unfolds the audience could visually read the chase vehicles being surrounded by more and more danger. That meant narrower tracks with steeper and higher cliffs. “All of this added further challenges with integrating the CG cliffs to the plate road and adapting/manipulating the scanned cliffs to look more perilous,” states Loch.

“We did receive a few notes asking for ‘Even more danger!’ which bought the cliffs close to being a vertical drop, these had to be done carefully otherwise you very easily lost the connection between the cliffs with the water. Once the cliff layout was signed off, a final scattering of foliage and rocks were added to give more complexity; this combined with a DMP pass really helped tie the CG elements into the plates. All the coastal environment shots were rendered with both CG water and atmosphere to ensure a more photorealistic look, on the closer shots – water plates were further integrated in comp to add to the realism and with the crashing waves they really added another layer of complexity and movement.”

Falling off a cliff

Ultimately the actions of all involved cause the helicopter to tumble spectacularly over the side of the cliff, along with Hobbs and Shaw. DNEG worked on some top side scenes right before the tumble which involved augmenting live action photography to add in a cliff edge, the cable and occasionally a digital helicopter.

They then generated the crash entirely digitally, aided by looking at extensive reference. “We looked at avalanches and building collapse where you see the scale of destruction and impact and heavy things crashing into soil and earth,” recounts Glass. “And we looked at helicopter crashes, too.”

DNEG took that reference and began its helicopter crash animation and simulation. The moment needed several iterations, says DNEG visual effects supervisor Mike Brazelton. “The very first test we did was just taking a chopper and simulating it falling down a mountainside. And it was very, very different to what we actually ended up with there. There were some story beats in there, some character performances, that they really wanted to get.”

“They wanted to have Hobbs on the back of the Peterbilt,” adds Brazelton, “and it was important to have the position he was in and all the movements during the fall – well, they were planned movements and they all needed to link up. We had to make sure that the chopper moved in a certain way to support all that. So it wasn’t as easy as just kind of simulating a chopper falling down a mountainside. It was more about the animation beats that you’ve got to get all of these pieces together.”

The other part of the tumble was working out how much dust, debris and rubble to generate. Too much and it covered up the actors and the set, and too little didn’t feel as devastating. “When we initially started out with the sims, the amount of dust and rocks that covered up the action, especially the characters, was too much,” says Brazelton. “You just couldn’t see what was going on. So we had to strip things back and make sure that you’re not just making cool effects. We’re there, really, to support the film and support the story.”

Things end up on a rocky facade, which was actually filmed on a set earlier in London. It had been lidar’d and texture photographed, allowing DNEG to replicate it in CG. This would be a set that DNEG had to blend its digital cliff into as a background for the final fight scene.

That scene capped off a daring couple of minutes in the film, summing up the kinds of effects so familiar with the franchise, telling many important story points and (only slightly) going over the top in the action. “That’s the trick with the Fast & Furious franchise,” concludes Dan Glass. “You’re constantly trying to come up with more and more outrageous ideas and yet keep them, somehow, credible.

Images courtesy of DNEG and Framestore © 2019 Universal Pictures. All Rights Reserved.

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