Director Alfonso Cuaron directs the new gritty drama Children of Men, and in the finest tradition of Blade Runner the future is a bleak and depressing place. For the visual effects team it is also a place filmed in long, complex, traveling single take shots with little or no 'set' lighting. The shots often required massive 3d tracking and compositing.

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 Children of Men is set in a bleak England of the future

Children of Men is not an easy film - then neither were the effects. It is often said that seamless effects are just that much harder than dramatic 'big' effects and this was the case with Children of Men. The effects ranged from complex tracking to digital photo-real births and babies.

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Digital baby

The effects work primarily went to Double Negative (DNeg) who handled most of the matte painting and futuristic compositing, including the extremely complex chase sequences. The digital baby was handled by Framestore CFC. All the work is impressive and the digital baby is perhaps the finest work of its type done so far.

A key moment in the plot finds the film's hero Theo trying to protect the heavily pregnant Kee to a place of safety. Passing through a strife-ravaged refugee town, Kee finds herself starting to go into labour. The pair take shelter in a bombed out hotel room. Sinking onto a mattress, Kee delivers the baby into the hastily washed, whisky-sterilised hands of Theo, who tenderly passes the newborn onto its mother's breast.

An animatronic baby was filmed on set. But as is often the case, it simply did not move with the behaviours of a real child. The decision was made to move the baby shots from digital enhancement to full digital replacement. This was both a complex 3D task and a complex tracking and compositing problem. The Framestore CFC 3D tracking department has 18 staff using a variety of 3D applications, including boujou, Matchmover and 3d Equalizer.


06Dec/cofm/childrenofmen3The birth scene used the same minimal lighting setup as the rest of the film and there were no special tracking markers. The stock was Vision 2 500T 5229 and was lit with a single bulb on a minimum exposure of T2, according to DOP Emmanuel Lubezki's story in American Cinematographer (vol87/12). The final digital baby moves considerably differently and is smaller than the more static animatronic baby. The live action version of the baby was limb-less as it was always planned to add digital limbs, but the Framestore CFC team needed to not only track the baby but digitally remove the places where the live action baby was not covered by the digital baby. Add to this the shot runs for three and a half minutes uninterrupted and it makes for an impressive result

Soon after work had begun on the delivery sequence, Director Alfonso Cuarón decided to go back to a number of shots featuring an animatronic baby that are seen later on in the film and replace the animatronic with the CG version in these shots. Altogether, Framestore CFC delivered 32 shots for Children of Men, with 20 of them featuring the baby.

DNeg worked on some 160 shots but this hides the amount of work they did as many of the shots were vastly longer than a normal shot in a fast cutting film. The longest shot lasts nearly 9 minutes.


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A significant part of DNeg's work was "futurizing" London. The DNeg tracking team had to place LCD style moving signage on everything from buses to billboards and street signs. This work was nearly all location work with green panels placed on real buses and places where the digital signs were to go. While much of the effects work was done on location, there were scenes such as the bus sequence which were filmed on a greenscreen stage. The entire background was added in post production using a modified version of the now famous DNeg advanced stitching tools, based on multiple camera background plates that were filmed from a roughly matching track.

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The special car and rig - notice the white support beams only 4 of which supported the full camera rig

For the longest DNeg shot, the plate photography was from location. Cuarón and Lubezki wanted to cover 12 script pages in one continuous take from inside a compact Fiat Multipla stuffed with five passengers trying to flee terrorist assailants on motorcycles. As little as a month before filming they were unsure as to how they were going to pull off the shot.

The car ended up being a special purpose car, built with a rig developed by Gary Thieltges of Doggicam Systems. It was piloted by a stunt driver lying near flat in front with space for another at the other end when driving in reverse. The car 'shell' was mounted to appear normal but with a complete rig overhead allowing the director and DOP to travel along above the actors.

One month before shooting, the first that Thieltges knew of the project was when he got a phone call from London, asking if he could rig a prototype setup to be tested in the streets of LA on Saturday. It was Thursday. With just 36 hours, Thieltges and his team set to work building the new H frame camera rig that would allow real time hot head pan and rotate joy stick control of the camera - and x and y tracking of the camera.


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The actors can be seen below the rig

The solution was to build a rig with two of Thieltges PowerSlides at right angles. The PowerSlides are incredibly carefully engineered and manufactured tracks with tolerances of under 1/2000 of an inch over 8 feet. These tracks each carry the high gear drive dolly rigs and wheels that allow the camera to seamlessly guide anywhere below the suspended H frame. These tracks combined with the rock steady Sparrow head 400 allowed the camera to move and film while remaining steady at speeds of over 120 miles an hour. It is the engineering and accuracy of the rig - coupled with the car rig - that Cuarón and Lubezki agreed would allow them to pull off their amazing shot.

The car itself was a small model Fiat Multipla with little room for the 5 actors to move, especially with a hanging Arri 235 film camera mounted from above also in the car cabin. The camera was on a two axis head Sparrow head 400 - which won the 2005 Technical Sci-Tech Award. The carbon fiber SH 400 combines extreme light weight, compact size and 400 foot film loads to provide remote operation in any situation and is a perfect choice for car mounts such as this. When Thieltges won the technical Oscar he stated “I started the design process of the Sparrow Head with a blank sheet of paper. I made a list of shots I had in my head that I had never seen on the screen. Then I designed the Sparrow Head to give everyone the ability to imagine and create their own list of never before seen shots."


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The Sparrow Head combined with the PowerSlide tracks

Thieltges points out that once they were on location "Alfonso was worried it was too stable. He even wanted to explore if we could loosen up the rig - as he joked that no one would believe it was really filmed live in camera - given how stable and precise the camera operation was". Once the director and DOP had committed to the approach they had no plan B and were completely committed to the Doggicam solution.

While Thieltges was in London to set up the production, it was his offsider camera operator Frank Buono who operated the camera during the weeks of filming. The entire Doggicam solution was so successful that the production insisted the rig remain in London for the rest of the shoot so the production could use it on other less demanding shots. "They said that after using the rig, going back to ordinary bonnet mounts and such was just going to be impossible" explains Thieltges.

The rig worked out to be less than 200 pounds including the Arri camera and 400 foot load. The team was able to rig the setup on the first day in under an hour plus lighting time. Running off standard 24v camera batteries, the camera unit itself is the smallest 1 piece camera unit available. It had already been used on films such as War of the Worlds and Poseidon but this was the first combined use of the Sparrowhead and the new H frame PowerSlides solution to produce such a flexible and free camera - while filming in such dynamic and real world environments.


It is within this filmed frame that the DNeg team need to track the shot to allow for digital motorbike stunts. In the shot, a bike races after the car driving in reverse and the real bike is swapped for a digital bike as it crashes. For obvious safety reasons the real bike could not crash into the film car with its star actors inside, so the bike transitions from a real stunt man to a digital one just at the point of impact.

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car plate shot
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Digital bike final shot

London's Battersea power station was combined with a bridge located over the M3 in Surry. Interestingly the power station sequence featured art from all over the world such as Picasso's Guernica from Madrid and The Statue of David. The scene also featured a giant floating balloon pig as a reference to Pink Floyd's The Wall and the cover of their 1974 Animals where the famous pig first appeared visible between the two front chimneys of Battersea power station.


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Bridge plate
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Power station background

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The final shot

You can see a movie of some results using the rig mentioned at the Doggicam Systems web site, then look for Two Axis Dolly.


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