Anatomy of a Batmobile chase: a Wētā FX round-table

The film’s stunning Batman versus Penguin chase includes some visual effects you might not even realize were there.

In what is one of the most spectacular sequences in Matt Reeves’ The Batman, the film’s hero chases down the Penguin along a stretch of Gotham highway. The scene sees the Batmobile dodging cars, escaping and even launching through fireballs, before ultimately causing his adversary’s Maserati to flip. The scene ends with Penguin’s upside down point of view as Batman confronts him.

To augment extensive practical car stunt sequences, production visual effects supervisor Dan Lemmon tapped Wētā FX for the job. The visual effects studio crafted several moments entirely in CG, while also adding in digital vehicles, explosions and rain to the live action plates. They also had to conceive their own in-camera effects in compositing to match cinematography by DOP Greig Fraser, who had covered camera lenses in silicone on set to simulate rain and dirt.

The team at Wētā FX was even called upon to replace Batman’s boots for part of that final walk the dark knight makes towards Penguin’s overturned vehicle, just one of the invisible effects tasks–his cape was another–that befores & afters learned about in this round-table with the VFX studio’s Anders Langlands (visual effects supervisor), Beck Veitch (compositing supervisor) and Dennis Yoo (animation supervisor).

Getting stuck into the scene with early blocking animation

Anders Langlands (visual effects supervisor, Wētā FX): The main thing for Matt was just trying to create this very high-impact, high-energy action scene, a thrilling car chase. He wanted it to feel supremely dangerous. It’s at night, it’s pouring with rain, there are cars slipping and sliding everywhere.

Matt is always most interested in realism, first and foremost. He also has a very keen sense of wanting to be able to follow the logic of things throughout the whole scene. He wants everyone to understand where everything is and how things flow, with one thing into the next thing for everything to make sense. So, one of the first things that we did when we got involved after they finished shooting, around the director’s cut time, was starting to do a bunch of postvis and blocking animation using the material that they shot to try and work out particular parts of the scene.

In particular, we did this for the huge pile up that happens towards the end of the sequence, when Penguin slams on his brakes and causes the truck behind him to slam on its brakes, which causes it to hydroplane, which then sets off this huge chain reaction of vehicles fighting against one another.

Dennis and his team spent a lot of time trying to work out those beats in a logical way so that the audience could follow what was going on and to tell the story of that happening. It was quite a quick series of cuts. I know that was a challenge in terms of, ‘How do we get these story points across in 10 frames or 12 frames?’

Dennis Yoo (animation supervisor, Wētā FX): It was really challenging. We were handed a first revision cut. They tried to shoot everything–it was pretty amazing what they gave us. But they wanted to find out what we could add in CG to get this story working. For us it was just more or less giving them an idea of what could be done and what couldn’t be done, but it was kind of like a puzzle to solve with all these shots.

They had this idea of that car chase, where the Penguin starts off this chain reaction to that final explosion. We had to help work out, how do you get from A to B with random footage that they actually shot? And so it was just filling in the gaps. We had a week to bash out a rough pass in postvis. They saw our first pass. It was a bit long, it was a bit off the mark, but at the same time, I think we were hitting some key points of the story and that got everyone excited.

Replicating reality, rain, and the ‘clown car’

Anders Langlands: They shot the main part of the scene, when they’re on the highway, at Dunsfold Aerodrome in the UK. They built a half mile section of highway on the runway there, with street lights going down either side and the central partition up the middle and had a whole fleet of vehicles. It was maybe 50 or 60 vehicles. Other parts of it were shots at Coryton, which is an oil refinery area elsewhere in the UK. They also ran a 360 degree ‘hydra’-like rig on a camera car to get background plates, which were intended for doing interior shots later on an LED volume with Penguin or Batman, although most of those ended up being bluescreen rather than LED wall shoots.

That was all great reference for us in order to build out background plates for various shots, or construct new shots out of essentially nothing but use the lighting reference. They did get a plate of some sort for basically every shot, even if we then ended up replacing them with fully digital shots, which was the case for a majority of the shots towards the end of the scene once the whole pile up starts.

Beck Veitch (compositing supervisor, Wētā FX): The lensing was really interesting on the sequence. In fact, we discovered quite early on this one particular shot just before Batman goes onto the highway, he busts through some pipes and you see this really amazing caustic flare from one of the lights. Recognizing that this was going to be something that we had to put into other plates and how the hell that we reproduce that in the first place was kind of cool and scary all at the same time.

We ended up finding out that there was one particular light that shows this flare that looks like a cross between a Nebula and some CG magical spell. And we found out how they did that, which was some sort of clear silicone sealant on a plate of glass, to give them this crazy caustic effect. So we went and shot a whole lot of stuff, which was really fun, because it was me and Anders putting goo all over glass plates and then running in front of the camera with a torch. We then integrated the caustics that we got from that shoot into a whole lot of the other CG shots.

Anders Langlands: Also, I think the biggest thing in the scene was rain more than anything else, which sounds like such a simple, boring thing when you say it, but it’s actually incredibly complicated to get right. If you’re dealing with a static camera there’s plenty of ways of doing rain, with elements or simple particle systems. Beck and I did a bunch of shots like that on War for Planet of the Apes for the start of the movie where it’s raining all the time. We mostly or entirely did 2D solutions for all of that.

But that all falls apart if you want to drive through it at speed because the rain isn’t coming straight down anymore, it’s flying into camera and it changes directions as the cars drive around. In particular, when you’re dealing with a very dark scene with lots of small light sources the rain then takes on a very particular texture. You don’t get just simple motion blur streaks, you get these textured broken up streaks caused by the oscillation of the rain droplets as they fall. It’s little spheres of water that are elongating and shrinking and wobbling left and right all around in weird ways, multiple times over the course of the camera shutter being open. And that gives you these beautiful, broken up textures. That’s the thing that really sells it as being real, it makes it look interesting.

We started working on this back when we doing War for the waterfall scene and we never really got there. So we set out to try and simulate it properly. The Manuka team came up with a rain primitive that allowed us to specify the different phases of the raindrop oscillation and how quickly they were going. And then that could be specified by parameters, which Christos Parliaros, who is our FX supervisor, set up on a particle system with Houdini in order to have them animate various different speeds.

It would calculate how the raindrops change shape over the course of the shutter being open, and the team wrote up a bunch of tricks to try and make that efficient to sample because very, very small, very, very shiny things is the worst possible case for a path tracer. We got something that actually looked really awesome. Unfortunately, it was still far too expensive to render. So, we had to go back in and create an approximation to that using old-school shader tricks which kept enough of the look to make it work, together with the overall simulation with the wind fields so that the rain was getting blown around by the wind and also affected by the cars as they drove through it. It worked out really well.

Then there’s not just the CG rain falling, but also the ground interaction and the mist and spray coming off of all the vehicles, because just adding all of those effects, both to the ground and also to all the vehicles, if you think about it, if you’re looking at a shot of a highway with a hundred vehicles on it, every one of those, in theory, needs to have a fluid simulation for the rain coming off with wheels for the spray. And that means that each one of those vehicles, if you are adding this to a live action plate, needs to be tracked. And all of those vehicles are different, so you need a different model for every single one of those, and suddenly this ballooning complexity gets completely out of hand. So we did a number of things, like…

Beck Veitch: …the clown car.

Anders Langlands: Yeah, the clown car. Our creatures team built what we called the clown car, which was essentially an adjustable car rig which we could give to the camera team to track. They could just move headlights and wheels around in order to fit it to whatever car happens to be in the shot rather than us having to go and try and build an accurate model for every car that they use and then figure out in an enormous pitch black plate which car it actually was in order to let the right vehicle track. That saved a huge amount of time there.

Beck Veitch: From a comp perspective, it was quite challenging because we were adding CG cars to a plate that already had a whole heap of traffic in it and a whole lot of spray in it. Ben Morgan, who was the lead on this sequence, and I did this massive deep dive into what rain actually looks like at night and through headlights. They also gave us a whole lot of amazing reference plates of where they had practical rain and where it was really wet on the ground.

This let us simplify stylistically what it looked like and how much detail we had to put into it to get the feel of rain on the ground and basically boil it down to where you see highlights on a road, or where you see crown splashes on the road which either take up a negative aspect to the highlights or a positive one where there’s no highlights. It came down to really simple stylistic decisions, but getting the feel of it was our main priority and actually really worked well.

Animating cars (and crashes)

Dennis Yoo: I had come off Mortal Engines, which had giant cities moving as vehicles. So I was used to having these crazy rigs in animation. On The Batman, our car rigs had this automated ground contact, so we could actually use the LIDAR scans, which were shot from the mini-highway that they actually made on set. That really helped out a lot just for understanding how the car’s wheels would be vibrating on the actual terrain that it was shot on. Things like that added to the realism.

Then, a big part of it was also the actual reference that we were given, which was from Dan Lemmon’s team. I don’t know how long they searched for this reference online, but we had to watch some pretty horrific crashes over and over. It was kind of creepy in a way, because you’re actually wondering if these people survived in the reference–some of the crashes were horrid. We could look at our motion and make sure that it was lining up with the actual stuff that was shot.

One of the challenges for us was trying to bring the danger back into the sequence. We tracked the actual cameras and we figured out that they were going about 15 to 20 kilometres an hour, which isn’t really dangerous speed. Luckily, Anders had a bunch of tricks up his sleeve. If it was a CG shot, we’d grab everything and speed up the camera. We’d travel a bit down the road further so that we could actually get to those speeds that we needed for the effects to start working and the actual tires to start bouncing.

Anders Langlands: There were definitely a few shots in there that were always planned to be CG takeovers, shots like the POV when Batman’s driving up the ramp, essentially to jump through the fireball. Here, they couldn’t get the camera car to go up the trailer. There was no way to do that safely, so that was always planned to be a CG takeover. They did basically set out to get a version of it shot pretty much, even if it was intended to go at least partially CG later. Which is great in as far as having a template to work from, particularly as a reference for lighting and compositing for the lighting and all of the lensing stuff.

In a lot of shots where we wanted to keep most of the plate, we might have CG vehicles put in here or there but essentially the shot was working as a plate. This was except for the fact that everything was moving too slowly. So, there’s a bunch of shots where we had to essentially move the camera faster and then render a CG road and then try and comp that in with all the vehicles in the plate. Which is obviously a little fiddly because you don’t want to roto 30 cars off of the road if you can help it.

We took judicious advantage of all the spray mist coming off of the wheels of the vehicles to hide the blend points. The funniest one for that actually was the shot at the end where you’re looking at Penguin over his shoulder with the fireball exploding in the background while he is cursing Batman out just before Batman comes back through again. The car Penguin was in–that Colin Farrell was in–was slowing down over the course of the shot and we wanted to keep it going at the same speed as it was at the start.

But, of course, if we’d moved everything more quickly, then the vehicles in the background that are on fire, the focus and shot would be receding from camera more quickly. It would completely change the composition of the shot because you’d get to the end and there’d be this tiny little thing in the distance, which you obviously didn’t want to do. So, in that one we did the same gag of just speeding up the camera, rendering the CG roads and then the vehicles in the background are actually just sliding along the road more quickly, but they’re staying in the same position in space. This was one of those things that came in quite late as a request and thank God it worked because I don’t know what we would’ve done. We got away with it.

‘Yeah, I got you! I got you!’

Anders Langlands: When the Penguin is looking back at the fireball and thinking he has stopped Batman, there’s a few main shots there we had to do. The first one is when we’re mounted on the nose of the Maserati, looking back at Penguin cursing Batman out saying, ‘Yeah, I got you! I got you!’ It was originally intended to be a much shorter shot. They actually had a stunt vehicle go over and explode in plate. It wasn’t actually the vehicle that ended up being in the scene. In the original version of the scene the vehicle that blows up is actually a van rather than the fuel tanker that we replaced it with. The trouble with the van was that the only way that he knew that it was carrying explosives was a tiny little warning sticker on the side of it, which of course you have no chance of seeing as an audience member when you’re watching the film. So, we replaced that with the fuel tanker. Actually, we replaced a slightly different vehicle with a fuel tanker throughout that whole part of the scene.

Because that shot was originally supposed to be shorter, they had a single explosion that happened which they did practically. We were always going to augment it, but the trouble was that Colin’s performance was so good that Matt wanted to just hold on it for as long as possible. It’s a really great moment and it sets up the following shots where the Batmobile comes through.

This meant we had to extend that fireball out quite a lot. We trawled through our elements library and used pretty much every explosion that we had in order to make a single explosive event into multiple explosions and this rolling fireball that carries on so that we can still believe that there’s a big fireball there when Batman jumps through it in the following shots.

Beck Veitch: Yes, we got practically every explosion that we had in our reference library and thank God we had a lot of them. But they were all on different stock. Some were shot on film, all different cameras and lenses and that sort of thing. Saki Mitchell, who comp’d a lot of those explosion shots, spent a lot of time going through them. We knew they were all going to be very de-focused as well, so it was about trying to get all of those at the same temperature and trying to even out all the colors.

Anders Langlands: It was one of those ones where we did a quick bash of it to get the composition and timing right and everyone’s like, ‘Yeah, great.’ And then you go back in and try to actually put it in the correct space in 3D and you realize it doesn’t actually quite work anymore. But you need the 3D because you need it for the correct de-focus and also because we have the CG road underneath and everything’s got to be reflected in that.

It’s a huge amount of work, not just with balancing, as Beck was saying, the color temperature of all the different explosions so that they look like what was shot on the day, but they were all different cameras, they were clipped at different intensities, they were shot at different exposures. They are all shot on practical cameras, so they were clipped at a certain point, too. But if we want to do reflections in the road, then we need to have a high dynamic range version of that. We’d have to go in and essentially gamma’ing things up and add all the range back in, in order to generate cards for Rachel Herbert who lit that shot to then reflect in the ground to get nice looking reflections.

Making a Maserati flip

Anders Langlands: In the scene, we cut to a wing mirror POV view. We’re looking in the mirror and seeing the Batmobile come through. That one was basically all practical, except for rain addition, and then we cut to the interior looking back at Penguin as he reacts to that, which was a fairly standard window comp. And then we cut to shots with the camera mounted on the side of the Maserati as the Batmobile comes through the fireball, lands, accelerates and then hits the back of the Maserati and sends it flipping over.

For the Batmobile landing, one tricky part was related to the suspension of the stunt car. The stunt car had very soft suspension so that it could land safely without breaking the neck of the stunt driver. So, it sort of bounced and it sat much higher than the regular Batmobile. So the first thing we had to do was chop the Batmobile off at the wheels. Actually, we ended up doing that in 2D, and then 2D animated to sit back down again, rather than springing up on the suspension.

Then we go into a re-time to speed up the Batmobile’s approach to the back of the Maserati, so that it feels like he’s going to hit him quicker. Then we take over to basically full CG for the Maserati as the Batmobile impacts and sends it flipping over. We did a pass of the Maserati going over and then obviously we had to take over the background at that point.

It was funny, one of the first versions that we sent from animation, in the tail handles the virtual camera seemed to freak out because it went under the ground. It was like an odd gimbal flip. But actually they loved that because it looked like we were seeing the nose of the car hitting the ground and then flipping over.

Dennis Yoo: It was deliberate! I had to mount the camera to the actual CG vehicle itself and then I realized, while flipping, that the camera couldn’t actually do that, that it was going through the ground. So I started animating the mount breaking and then flipping out that way, which I didn’t know you guys thought was the gimbal. The good thing was Matt really liked it.

Anders Langlands: Then we take over from the practical Maserati to a CG Maserati. There were a couple of interior shops of Penguin rolling around inside, which was actually on a rotisserie rig on a rotating gimbal that spun the car that Colin was in. I think it was quite a nauseating experience for him because it really was actually spinning around like crazy.

Dennis Yoo: For the flip, part of it was trying to keep it physically real. We try not to cheat as much as we can. Once you start cheating, then animation always gets called out for cheating. The animator who animated this one, Andrew Silke, he’s quite a veteran, so it was amazing having him on the team. He busted out a few different types of spins and flipping, but the reference that we mainly used was Casino Royale.

Anders Langlands: What everyone liked was the energy of it and obviously almost half of it was real, where they actually did that to the car. So that was a touchstone for what we were aiming for.

Dennis Yoo: Part of the challenge in this particular shot, too, was that the camera was still attached to the plate. It’s always a challenge when you have a handover camera and you’re trying to do something that everyone thinks should look right. Which is, the Penguin’s car going right over the Batmobile, but in CG, the car actually does a little bit of a ‘U’, because it’s the only way it looks like it’s going over the car.

Anders Langlands: You never told me that.

Beck Veitch: We never tell you when we cheat.

Dennis Yoo: We also tend to have different types of tools while we’re animating, knowing that there’s going to be FX sims added, like a gravity ball that we put in our scenes to make sure that the gravity’s working. We actually use element cards as well, which is obviously tied to realism and so putting that in our scenes grounds us to the reality of the real world.

Anders Langlands: For the flipping there was a whole bunch of destruction, which Christos Parliaros worked on, generating all the elements for everything, like the car falling apart as it rolls and all the extra glass and debris. All of the spray that’s coming off of the back of the Batmobile as it’s sliding around to come to a stop is all digital, too. That’s all fluid sim.

Batman’s boots and Batman’s cape

Anders Langlands: Then there’s the key shot of Batman walking up to the Maserati. You’d never know watching the movie, but, Beck, you should say.

Dennis Yoo: Yeah, Beck should explain.

Beck Veitch: Well, the shot of his boots. What he wore in that scene were these boots with really dark zips, and they were really reflective chrome-y zips and Matt hated them. I loved them. I wanted a pair of those boots! But we had to get rid of the zips and we were at first thinking, ‘Oh my God, we’re going to have to do CG,’ but…

Anders Langlands: …Beck’s like, ‘Don’t be stupid. I’ll do it.’ And then you did.

Beck Veitch: It’s totally a 2D hack. It was really hacky.

Anders Langlands: No! It was really smart and super crazy.

Beck Veitch: I love a good hack. In fact, this whole project, it always felt like to me, that we were thinking outside the box while flying by the seat of our pants. Because he’s walking past camera, I stabilized each boot from ankle to the top of the boot and then patched something over it and then re-tracked it by re-applying the tracking motion. It was actually quite a simple solution. I like a simple elegant solution as opposed to a very convoluted one. I was very lucky that actually worked. Because otherwise, it would have had to be CG boots.

Anders Langlands: In all of those shots, too, Batman’s cape is CG. They had a rain machine out for the scene, and with a practical cape, well, when you get a big piece of cloth soaking wet it doesn’t tend to do the most exciting things in the world. It would just be hanging down straight, like a solid lump. So they actually took the cape off for those ones and we did CG cape to get the most heroic moment of the cape billowing out in the wind as he’s walking up towards Penguin.

There we are also upside down in the car and you see Batman silhouetted against the huge fireball in the background. The challenge is that if you’re adding a big dark material behind Batman then we have to rebuild all of the flaring around the images. So that ended up being basically CG. I think we kept his head but the body was mostly the CG one, at least patched in.

Beck Veitch: It was patched in. We had to get rid of his edges where the flare was over his edges in the plate. So, we had to patch in CG arm and torso edges.

Anders Langlands: I remember seeing someone on Twitter posting, ‘Look at this.’ They had a behind the scenes photo where they’d taken a picture of Rob or his stunt double in the rain before they decided to take the cape off. The person was saying, ‘Look, no CG.’ That’s always funny if not gratifying when you see that sort of thing.

A final thought on ‘kissing bridges’

Beck Veitch: I have to mention kissing bridges. So, every film that Anders and I have worked on together, I have ended up comp’ing a kissing bridge. So on Apes it was in the fortress when Blue Eyes and Lake get back together. On Alita it was Alita and Hugo kissing on the bridge in the rain. And then on Mulan it was the end of the film where there’s another kissing bridge. Romance is not my favorite thing in the world, explosions are. But I always seem to end up comp’ing every single kissing bridge. Then, on this film, there was no romantic encounter for us like that, but Anders did do a fabulous Banksy-esque graffiti which is hidden inside a bridge.

Anders Langlands: [laughs] Yes, we have a bridge in the form of the overpass that the container truck smashes into.

Beck Veitch: Paul Redican, who comp’d those shots, put Anders’ bit of Banksy graffiti of, what was it, two policemen kissing?

Anders Langlands: Yeah, I did a homage to the famous Banksy ‘Kissing Coppers’ graffiti, but with Gotham cops instead of British Bobbies. That’s graffitied on the side of the tunnel, if you look really carefully. I don’t think you can actually see it in the final frame because it’s so dark, but we know it’s there.

Beck Veitch: We know it’s there. That’s our kissing bridge.

Source-https://beforesandafters.com/2022/04/01/anatomy-of-a-batmobile-chase-a-weta-fx-round-table/