The Dark Knight is a masterful film. There are brilliant performances, great direction and some magnificent visual effects. This week we cover lead facility Double Negative about their impressive IMAX batpod shots and how their work fits so seamlessly into this powerful dark masterpiece.

Many excellent companies worked on the filmThe Dark Knight. The miniatures work of New Deal are faultless and the face work of Harvey Dent done by Framestore is haunting. But in this week's podcast we focus on the work of Double Negative and drill down on the Bat Pod motorbike chase and the complexity of finishing much of the work at 5.6K IMAX resolution.

IMAX

The visual effects work is all the more impressive in this film given the format and resolution that many of the visual effects were completed at. About 20 minutes of the film are presented in IMAX format, when shown in an IMAX cinema. The film unusually moved between an up-rezed IMAX 1.43: 1 scope 70mm projection to a full 1.33:1 IMAX format scene to scene in the film's IMAX prints. Surprisingly, the different aspect ratios cutting is not annoying or distracting. This is the first time a major Hollywood film has shot large sections of the film in the 15-perf, 65mm horizontal load IMAX format. Films have been up-rezed before, but not shot and finished with whole sections as full 8K scanned visual effects sequences. The result is breathtaking.

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Heath Ledger shines as The Joker

The production, for the most part, treated the IMAX camera as a normal 35mm camera, but the aspect ratio being more square, and the viewing experience so different - framing had to be adjusted. When a normal 35mm print is made, the filmmakers take a cut from the IMAX print and so the whole film is presented normally, but of course with superior resolution, grain and optics.

Just as moving from HD smaller sensors to full grade sensors introduces a shallower depth of field and a more filmic look, the move from 35mm to IMAX produces an even shallower depth of field. In many of the close up IMAX filmed shots, the actors nose would be in focus while their ears were already out of focus. In an American Cinematographer article, the 1st AC Bob Hall described shooting on the IMAX MSM9802 and Mk III cameras with Hasselblad lenses as having "extreme wide shots with the depth of field of a telephoto shot".

Not only did the depth of field optics change but due to its bulk, a standard 500ft film load lasts about 100 seconds at 24fps. The film's IMAX processing and 35mm to IMAX up-rezing was handled by DKP 70mm Inc. in the USA. The final filmout combined the up-rezed, 4K DMR film out, 5.6K and 8K IMAX film outs into one massive 70mm print.

Bat-Pod

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Much of the Bat Pod were filmed in IMAX format from the back of a specially modified Mercedes SUV

To film the action Bat Pod sequences in IMAX, the team filmed from the back of a specially modified Mercedes SUV with an Ultimate Arm-Lev Head combination. So dramatic was the filming of the Armed car chase that a full IMAX camera was crushed and destroyed during filming as you can hear in this week's podcast with Double Negative's Paul Franklin. Double Negative (DNeg) was the lead effects house on the film and did most of the visual effects in the chase sequence.

While the Batmobile gets a good run in The Dark Knight, and DNeg did digital car work, the film introduces Batman's newest ride, the Bat Pod, a high-powered, heavily armed two wheeled machine. "Of course we were going to have the Batmobile back," stated Director Chris Nolan, when talking to the press "but we wanted to give Batman something new: a fresh means of transportation, something very exotic and very powerful looking. It's a two-wheeled vehicle, but it's definitively not a motorcycle. In essence, the Bat-Pod is to the world of motorcycles what the Tumbler is to the world of cars."

In the Armed car chase, special effects company New Deal built a scaled model tunnel with a camera mounted on a moving side platform. The miniature truck and Batmobile were remote controlled and this staged miniature shoot was carefully intercut with both first unit and completely digital shots from DNeg. Paul Franklin is quick to point out just how good the New Deal work was and how little they needed to add to the miniature shots. "We added smoke and tire effects only," he comments.

Double Negative was required to seamlessly extend the in-camera action and provide some key dramatic moments - all done at full IMAX resolution. The shots involved a wide range of standard VFX tasks - rig removal, background cleanup, greenscreen inserts etc. - but the two biggest challenges were the Batmobile Death/Bat Pod Birth sequence on the underground freeway and the set of fully digital shots on La Salle Street during the chase climax, as in the end, the situation gets the worse of the Batmobile and it is completely ruined.

The actual final crash was created by SFX supervisor Chris Corbould's team. Batman tries to restart the Batmobile to rejoin the chase, but the car is totalled so he instead activates the eject sequence that releases the Bat Pod (the bike is formed from the Batmobile's front wheels). Initially, the plan was to work with plates of the crashed practical car, adding breakaway panels during the ejection and a quick flash of the digital bike before cutting to the practical bike. However, as the sequence developed it became obvious that the available angles on the practical car were not fully telling the story, so it was decided to create a fully digital replacement of the Batmobile and Bat Pod and their surrounding environments.

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The Bat Pod only one stunt man could actually ride it

The DNeg team were given a large amount of access to the crashed Batmobile after it was no longer required for filming, allowing them to work up a highly detailed digital model which would hold up to intense scrutiny on the IMAX screen – in many ways the digital version had more detail than the real thing as a lot of extra detail was created inside the vehicle that was revealed during the ejection. The animation involved a combination of hand-keyed action and an extensive secondary dynamics system that added the broken wobbles and gyrations of the damaged car. For the final ejection the panels were blown off the car using dnDynamite, DNeg's proprietary rigid body dynamics system and the Bat Pod's swerving journey was enhanced with smoke and dust elements created with a combination of Maya fluid dynamics and dnSquirt – Double Negative's new in-house fluid dynamics toolset. All smoke and dust was rendered with DNB, DNeg's volumetric renderer.

The final element in the sequence was the environment itself - most of the underground freeway moments were shot on Lower Wacker Drive in Chicago, but key moments - such as the crash itself - were filmed on the large stage at Cardington in the UK. Whilst looking very similar, the two sets had significant differences so the digital model had to incorporate aspects of both as it bridged the gap between one and the other. Initially, the environment was created from re-projected plates, building only simple geometry, but as the sequence developed and the camera moves deviated further from the angles in the available plates, it was decided to go with a fully digital build of a long section of the underground freeway created from a combination of survey data from both locations.

Fast and maneuverable through the streets of Gotham City, the Bat Pod has the same monster truck tires as those found on the Batmobile. Well outfitted for hostile situations, it is equipped with weapons on both sides: 40mm blast cannons, 50-caliber machine guns, and grappling hook launchers. The Bat Pod is formed like a phoenix from the crushed carcass of the Batmobile. In the sequence leading up to this and following it, the filmmakers used every trick in the book to film the action sequences.

The original design of the Bat Pod was the brainchild of production designer, Nathan Crowley, and Director, Nolan.
With little more than the basic concept in mind, the two retreated to their favorite design headquarters—aka Nolan's garage—to work out the details. Crowley recalls, "We figured, 'Let's just go for it; let's build it full-size.' So we did. We got some tools and put together a full-size model out of anything we could find that might fit."

Of course, Nolan and Crowley still had no idea if their invention could actually run. That's where the special effects team, headed up by Chris Corbould, came in. Corbould relates, "First of all, I remember when Chris Nolan first showed me his idea for the Batmobile. I had no idea how we were going to make it work even though it ended up being very successful. So when I got his call asking me to come have a look at something he called 'the Bat Pod,' I thought, 'Uh-oh, what have you dreamt up this time?'"

Corbould flew to L.A., and arrived at Nolan's garage to view their creation for the first time. "I think he was almost in tears," Crowley laughs. "He looked horrified that he might have to actually mechanize that thing. We kept bringing him cups of tea, and he was just sitting there staring at it, looking like, 'Oh my God, what time is the next flight out?' It was the usual clash of design versus engineering."

As it turns out, Crowley was not far off in his assessment of Corbould's state of mind. "I was flabbergasted," Corbould admits. "I stood there silently, pretending I was mulling it over, but the thought going through my head was that they both had to be off their nut. Where was I going to put a power train? And with those massive wheels, would this thing actually steer? There were so many issues."

Despite his concerns, Corbould returned to London, where he and his crew began brainstorming ways to bring the Bat Pod to life. After some trial and error, they developed the final working Bat Pod, which was surprisingly close to the rough model that Nolan and Crowley had originally constructed. Nolan confesses, "It really shouldn't
work, but somehow Chris and his team found a way to do it."

"The funny thing is," Corbould says, "I don't think Chris or Nathan had ever ridden a motorcycle in their lives, so they were completely unaware of the mechanics needed to get that thing moving. In a way it was beneficial because they weren't steered towards a more orthodox bike, even subconsciously. The fact that they had no knowledge of
the mechanics helped them create this weird, wonderful vehicle." Actually being able to drive it was another matter entirely. Nolan confirms, "The finished product that Chris and his team came up with was very striking, very effective and worked very well, but it's incredibly difficult to ride and to steer."

In order to maneuver the Bat Pod, the driver has to lean his upper body forward, almost horizontally, and steer from his elbows, rather than his wrists. In fact, the only person who was able to master the Bat Pod was professional stunt rider, Jean-Pierre Goy. Corbould offers, "I've worked with Jean-Pierre a couple of times, and he is one of the best bike riders in the world, if not the best. Right away, he totally got in the mindset of learning that machine. He said, 'I'm not riding another bike until I finish this sequence,' because he had to concentrate on the Bat Pod's unique handling qualities. I'd be lying if I said it was easy for even him to ride, but it looked spectacular when he did, so it was worth the effort."

The Truck

As it had in Batman Begins, the city of Chicago once again became Gotham City. "I spent some time growing up in Chicago," said Nolan, "so it's a city I know and love. It is famous for its architecture and it is also a very film-friendly city. We shot there for weeks on Batman Begins, but this time we were going to be there for months and the help and encouragement we got from the city was extraordinary." Chuck Roven confirms, "I can't say enough about Mayor Daley, the Chicago Film Office and, most importantly, the citizens of Chicago, who could not have been more excited or more welcoming to us. They gave us total cooperation and allowed us to do some unbelievable things on their streets, and we appreciated and always tried to respect that privilege."

The Dark Knight is set in the same universe established by Batman Begins and many of the details such as the Batmobile are the same as in the earlier film. The Dark Knight, however, is even more firmly rooted in an observed, recognizable reality than Begins. Gotham looks much more like a regular city, and even the raised train lines so featured in the first film, are only seen in 2 shots according to Franklin.

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In the armed car street chase scenes many shots required complete digital building replacements

Creating Gotham City for the Dark Knight provided a number of new challenges for DNeg, above and beyond those that had been tackled on Batman Begins. Whilst working on Begins, Double Negative developed a photographically-led digital architectural environment pipeline, which was used to create extensions to live action environments as well as completely CG cityscapes. This pipeline continually evolved while being used on other films such as World Trade Center and Harry Potter and the Order of the Phoenix.

DNeg's biggest hurdle on The Dark Knight was to overcome the massively enhanced resolution of the IMAX shots (5.6K). The team started by refurbishing all the assets that had been built for Batman Begins - cleaning up the geometry, repainting the textures etc. For the earlier film, the buildings were made for either day or night work, and only the Monorail system and Wayne Tower worked in both environments. For the Dark Knight, however, all items were set up to work in full daylight, magic hour (twilight) and full night time. This gave tremendous flexibility with the architectural library, allowing for the quick extension and enhancement of any shot that required it. On Begins the digital architecture played mainly in wide shots or in the far distance, whereas on the Dark Knight there was a much higher percentage of close up shots of the buildings, so a set of super-high quality structures were developed that played in the helicopter crash sequence as well as in the Bat Pod/truck chase.

Inarguably the most incredible thing that the City of Chicago allowed the production to do was unprecedented: flipping a 40-foot tractor-trailer, end over end, right in the heart of the city's banking district on La Salle Street. While DNeg worked on this shot, it was only to paint out the "telegraph pole" that the production shot down with Nitrogen canons to cause the flip, and some road clean up. This amazing shot was almost entirely done in camera explains Paul Franklin. Although Franklin was on set, standing to one side next to Heath Ledger (in costume) to watch the stunt on the night, Franklin gives full credit to the special effects team for an incredible stunt.

According to the film's production notes, when Chris Corbould saw the truck flip described in the script, he admits, "I tried to make compromises with Chris—like maybe the whole truck doesn't go over or maybe we could use a smaller truck—but he wasn't having any of it."

Nolan responds, "Finally I turned to him one day and said, 'Chris, it really ought to be an 18-wheeler. And I know you can find a way to do this because that's just who you are and that's what you do." The first order of business was to make sure the stunt was even possible. "After about six weeks of calculations, we were ready to do an actual test," recalls Corbould.

"We went out to an open space, got the truck up to speed and pressed the button, and it just sailed over. I had to go to Chris Nolan and tell him it worked perfectly." Nevertheless, the filmmakers were aware that there was a vast difference between flipping a truck in the middle of nowhere and doing it in the middle of a city street. Before they could carry out the stunt, city engineers were called in to make sure that the tons of force necessary to send the truck end over end would not damage the infrastructure of La Salle Street, including the various utility lines that run beneath it.

Once safe parameters were determined, the production was given the green light. When the night of the stunt came, the truck flip went like clockwork, earning applause from the assembled cast and crew. "It was an impressive thing to watch this truck fly over and land precisely where Chris said it was going to land," Nolan remarks.
"At the top of its arc, it looked almost like a skyscraper standing there, and then it just continued going over very gracefully. I've never seen anything like it."

This sequence was filmed on IMAX format, and in an IMAX theatre this is one of the most impressive sequences as it takes full advantage of the much greater vertical height in the IMAX format.

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Director Christopher Nolan on the set of Warner Bros. Pictures and Legendary Pictures The Dark Knight
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Director Christopher Nolan, hands folded leaning on rail, watches as Christian Bale prepares for a scene on the set

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Director Christopher Nolan and Aaron Eckhart on the set of Warner Bros. Pictures and Legendary Pictures The Dark Knight
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The cape was one of the few assets that did not need to be digitally updated for shots requiring digital doubles in this film. Most of the rest of the suit was modified, but not the cape

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Director Christopher Nolan, Michael Caine and Christian Bale on the set
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Director Christopher Nolan on the set


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