The Hobbit’s 3D wizardry

  • Director Peter Jackson (left) allowed PM to visit the set of The Hobbit to observe the film’s motion-control system. Here, Jackson reviews notes with Martin Freeman, who plays Bilbo Baggins.
  • It’s no small feat to make the wizard Gandalf appear larger than his dwarf and hobbit friends. Illustration by VIGILISM
  • The actors were daunted by the technology, Martin Freeman says, until they saw how well it worked.
Date:1 February 2013 Tags:, ,

Forget sorcery. To shrink his movie’s cast to halfing size, director Peter Jackson brewed up a digital solution. By Eric Vespe

Peter Jackson has always loved the magic of moviemaking. After watching the 1933 classic King Kong at age 9, he started shooting stop-motion films with his family’s Super 8 camera. Three years later, he carved up an old fur coat that belonged to his mother and used it to create a model of the great ape. In his early 20s, the budding director was baking latex moulds in his mother’s oven to produce the prosthetic hands and heads for Bad Taste, the homemade horror flick that earned him a trip to Cannes in 1987. But the eclectic cast of characters in the Lord of the Rings trilogy truly put his powers of invention to the test.

To make the wizard Gandalf appear considerably taller than his on-screen colleagues, Jackson employed a number of tried-and-true cinematic tricks. In one scene, he used a custom-designed wooden cart to position Elijah Wood (Frodo) far to the right and a few feet behind Sir Ian McKellen (Gandalf) and recorded the action at an angle that made it look as if the two actors were seated side by side. In the Hobbit trilogy, Jackson’s latest tribute to the mythic Middle-Earth world created by author J R R Tolkien, such sleight of hand was not possible. “Once you shoot in 3D, it completely blows your cover,” he says. “Your forced-perspective tricks are naked to the audience. With 3D glasses on, they can see exactly how far away the characters are.”

This left the director with only one alternative: to conjure a community peopled with hobbits and dwarves, he would have to resort to the cumbersome process of filming man and halfl ing separately and uniting them digitally in postproduction. Jackson had occasionally used that technique in The Lord of the Rings, but The Hobbit was filled with dialogue – often two or three script pages in succession – between Gandalf and his pint-size pals. “It’s very difficult for them to have a conversation that feels natural,” says Jackson, citing his early attempts to unite the wizard with hobbits. “We would have Ian do half the conversation and then Elijah would have to fill in the hole Ian had left him. It was a stilted way of doing it.”

So before filming began on The Hobbit, Jackson asked his team to come up with a better approach: one that would allow him to direct every scene in real time. The answer
arrived in the form of an innovative motion-control system.

Instead of shooting the actors one at a time, the director placed them on two different sets 15 metres apart and recorded them with different cameras. The live, or master, rig was outfitted with encoders that measured the pan and tilt of the camera, the motion of the boom that held it aloft, and the speed and movement of the dolly beneath the whole set-up. This data was crunched, scaled and instantly relayed to a slave-rig camera on a green-screen set, allowing it to move on three axes in perfect harmony with the first.

In this way, Jackson could place the slave camera much closer to Gandalf and, with the magic of software, remove the green background and merge the images from the two sets so it appears as if the wizard towers above the dwarves. One challenge was to create a green-screen set that precisely mirrored the live set – archway, walls, chandelier, etc. If Gandalf rested his hand on a green-screen table, it could not appear to float above the top of the table on the live set.

To precisely position everything, the crew invented a device called the Pinger. Think of it as a laser-beam protractor: it measures distances and angles, allowing the crew to pinpoint the contact spots common to both sets. Once those spots were aligned, the live set and slave-set cameras worked together to generate the proper perspective. The system included a monitor that supplied Jackson with a live composite of the two shots so he could watch the scene unfold. The actors on both sets used green tennis balls to locate their sightlines and hidden earpieces to follow the dialogue.

In the system’s trial run, Gandalf pays a visit to Bilbo’s Bag End home with a company of dwarves clustered around him. In the course of the shot, he has to duck below an archway, bump his head on a chandelier, greet each character by name, lay the dining room table with forks and knives, and accept a cup of wine from a cohort.

The live set was built to human scale.
The table, the plates, the drinking cups were all of normal size since they would be filmed next to average-size actors. The items on the green-screen set were scaled down by 25 per cent. In Gandalf’s hand, the wine cup looks tiny. But because the slave camera was placed closer to him, the cup and the hand both appear much larger on film. In fact, when the two images were combined, the cup looks exactly like those in the hands of the dwarves.

For the two shots to blend seamlessly, everything Gandalf interacted with had to be represented in some form. The scaled down table and archway were green, the knives and forks looked like those on the live set, only smaller. Because the wizard had to bump his head on the chandelier, it was scaled down and placed on the green-screen set. Green boxes indicated walls and corners to help McKellen visualise the geometry of the room. The cup of wine was presented to him on the end of a green stick at the very moment that an actor on the live set was handing a second glass to another green stick.

“There was a lot of inventing going on,” says motion-control supervisor Alex Funke. “We were figuring out how to do stuff as we went along. It wasn’t just taming the software, it was finding the tricks that made the system fly, made it work convincingly.”

Even with the Pinger, for example, the crew soon discovered that when you enlarge Gandalf to make the world look smaller, the floor seems to rise up too. This made for awkward compositions with McKellen floating above the ground or sinking down into it. To solve the problem, the crew built platforms for him to walk on. But since that proved to be far too time-consuming, the team came up with yet another innovation.

In essence, Jackson’s technical wizards found a way to shift the whole world inside the brain of the motion-control system without it noticing the change. To grasp the complexity of that challenge, it helps to understand how the system’s co-ordinates were compiled. The lift and swing of the boom were measured by monitoring the rotation of gears affixed to the rig of the live camera. The dolly’s movements were measured by a skateboard wheel mounted on a spring-loaded spar beneath the chassis. After the data was collected, the motion-control system did the maths, plotted the shot sequence on the three axes, and relayed this information to the slave camera in the form of sync pulses.
You can’t just offset the camera. If you do that, you’re completely disrupting the mathematics that make those Cartesian co-ordinates work. But you can fool the system. Thanks to an ingenious device called the Knob Box – whose means of operation remains top secret – Jackson and team could tweak by hand any slight miscalculations on the slave set without causing mayhem to the 3D effect. If the archway was out of line by a fraction of a centimetre, they could fiddle with the rig’s north-south axis without upsetting the scene’s complex choreography.

It took time to work out all those bugs. In fact, Jackson still jokes about the headaches he endured during the technology’s trial run. “It does represent the only time in my filmmaking career,” he says, “that I spent an entire day shooting a scene and didn’t get a single frame of film.” But everything went much smoother on day two. The crew wrapped up the shot before breaking for lunch. “At first, we were all quite daunted by (the technology),” lead actor Martin Freeman says. “I just thought, are these people mad? That will never work! And then I saw a cut and thought, yeah, it really does work. It works amazingly well.”

These days the director likes to marvel at how the technology rescued him from having to pre-program the camera, which in turn allowed the operator to respond to the pace of the action. “That was one of the joys of it,” Jackson says. “You didn’t have to think about the trick anymore. If you wanted to crane, dolly, move in, move out, or have characters come in and out of the frame, designing the shot was just as it would be on a live-action set.”

In the end, Jackson’s latest stab at movie magic is invisible, and that’s a good thing; it freed the actors to provide the drama. In the slave-motion control scenes, the director shot 10 to 12 takes – and every one of them was fresh.

How it works: The Hobbit’s motion-control system

It’s no small feat to make the wizard Gandalf appear larger than his dwarf and hobbit friends. In the past, director Peter Jackson had to shoot characters of different sizes at different times and piece the scenes together in postproduction. “There was no way to direct the whole scene at once, no opportunity to nesse performances,” says motion-control supervisor Alex Funke. With the new system, Jackson watched scenes from The Hobbit unfold in real time.

  • Instead of shooting the actors at different times, the director recorded them with cameras on two different sets. This allowed him to position the lens much closer to Gandalf, raising his stature. By placing the actor on a green-screen set, the director could digitally remove the background and merge the two images.
  • Digital encoders on the Aerocrane measured the lift and swing of the boom, the speed and movement of the dolly, and the degrees of pan and tilt. The data was funnelled to a motion-control system with software especially designed to scale the information down and relay instructions to the slave side.
  • When the Genuex crane received the instructions via its own motion-control system, the servo motors – fast, silent, and accurate – on the crane’s dolly carried them out.
    The Genuex mirrored the actions of the Aerocrane, but each movement was scaled down because the camera was closer to Gandalf.
  • The film’s video assistant system was a marvel capable not only of recording the digital feeds from all four cameras (two on each rig for 3D effect), but also of combining them into an image Jackson could review. His takes often stretched to 12 000 frames. That’s close to 2 terabytes of data per shot, Funke says.


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