A future metropolis, slow motion gun battles and some literally head-exploding scenes - these are just some of the visual effects in Pete Travis' Dredd 3D, a new take on the 2000 AD Judge Dredd comic character. We go behind the scenes of the stereo effects work in the film with overall visual effects supervisor Jon Thum, Prime Focus World, Baseblack and The Mill.

Slow motion effects formed some of the film's key sequences.

Thum, VFX Supervisor of Dredd 3D and Prime Focus World, was on-board early in the concept stage working with writer and producer Alex Garland. "Alex wanted Dredd to be gritty and real and visceral," says Thum. "There was a lot of violence in the script and he wanted that to come through, except for the drug moments when it needed to appear hyper-real and somewhat beautiful."

Adding to the impact was the fact that Dredd was a stereo show, filmed natively on RED One's and SI-2Ks, and high speed photography shot on Phantom Flex's. The majority of principal photography - around 95% - was filmed in stereo, although helicopter plates and some other scenes were post-converted by Prime Focus, and some native stereo was also 'exaggerated' in post. "Our DOP Anthony Dod Mantle was really excited about shooting in stereo and that was one of the big things that brought everyone together," says Thum. "He would experiment with things out of focus which is usually a big no-no, but we really set out to break the rules, or see how we could break the rules. We talked a lot about filling the scene with objects and production design took that on board, so you'll see all the sets have mid-ground things jutting out and hanging from the ceiling."

- Above: Jon Thum, VFX Supervisor of Dredd 3D and Prime Focus World, explains the work behind Dredd's futuristic landscapes. Courtesy of our media partners The Daily.

Making a mega-city

Needing a suitable location in which to shoot a gritty cityscape for the film's setting - in which law enforcers like Judge Dredd (Karl Urban) have the power of judge, jury and executioner - the production chose Johannesburg and Cape Town. J'burg would form the basis of Mega-City One, a futuristic metropolis inhabited by 800 million residents and featuring enormous tower blocks stretching up to a kilometer high or 200 stories. A newly built studio space in Cape Town served as interiors for the film's primary scenes which take place inside Peach Trees, a soaring tower block taken over by the mafia - including Ma-Ma (Lena Headey) - and the base for the production of new street drug Slo-Mo.

Mega-City One.

For exterior shots of Mega-City One, ranging from wide vistas to backgrounds for a street level vehicle chase, the filmmakers relied on designs from visual effects art director Neil Miller and the art department. "It had to feel like these things had risen out of the old city," explains Thum. "You also got a much better feeling of scale if they were separated by distance. Also, it had this tombstone feeling when you went into wide shots."

At the design stage, small outcrops and appendages were added to the buildings to break up straight lines. "We thought it would be cool if these mega blocks had some outside space that kids could go onto to play basketball or skate," says Thum. "It was a great way to give some scale of the city looking down - you'd see this skate park and realize you're half a kilometre in the air. And then it became a plot point where the characters escape to for a short while."

Chase scene through Mega-City One.

A second unit helicopter shoot over Johannesburg served as plates for the wide shots of Mega-City One. With only last minute flight permissions given, Thum was unable to go in the chopper for the filming, despite having designed many of the planned vistas. "In the end, all the helicopter shots we used were shot non-specifically," he says, "and I just went through them and picked out the ones I thought would tell the story. It was just the nature of the hectic shoot we had."

Prime Focus handled the digital augmentations to the Johannesburg plates, adding in the tall towers and also removing whole blocks and replacing them with CG freeways, traffic and atmosphere to give the city a much more claustrophobic feel. "We figured we could build a certain amount of buildings and re-use them," adds Thum. "So we had four or five hero buildings that we textured up really well starting with photographic reference of buildings around town. Then we had eight or ten mid-ground buildings that were fairly low-res and didn't have that much detail. And then another level that was just a shape in the background."

Watch behind the scenes of the chase scenes in Dredd 3D. Note: no sound in this clip.

"We would render it with the right lighting from the J'burg plates and then after that we would then paint and re-project extra details," adds Thum. "Anything like graffiti or lights were painted on afterwards once we had the shot in front of us, just to add that extra level of detail and credibility. That's also how we did the atrium and the interior - we'd re-use bits and paint and re-project different details. It let us make very quick changes to how it looks in the final shot."

Thum also contributed an additional aspect to the Mega-City One shots that had not originally been planned. "We had an early cut that was close to finished," he says, "and Alex asked me was there anything else we should add visual effects wise - any things that might add a lot for not much money. I came back and suggested the drones in the sky. I thought, 'What if we had surveillance aircraft that could tie in all the stock footage and the car chase?' It ties in also with the control center we saw in the film."

Inside Peach Trees
Anderson and the interior of Peach Trees.

Several of Dredd's key sequences occur in the atrium of Peach Trees, a vast central congregation area for the building's residents surrounded by stores, with views up the center of the tower. It is here that Judge Dredd and rookie Anderson (Olivia Thirlby) arrive to investigate the murder of three men, thrown from high above by Ma-Ma's henchmen after being skinned alive. The Judges then become cocooned inside by Ma-Ma and the building's defense systems.

"The production was struggling at one point to find an atrium to shoot in," recalls Thum. "We'd designed a 40m x 40m area for these guys to get thrown down, so we needed space that was at least as big as that. There wasn't a shopping center or mall in Cape Town or J'burg that was big enough and they didn't want to build an expensive set. But at some point during the reccy's we were getting photographs back from Cape Town, and we noticed a little space in the background. We looked on Google Earth and found a sheltered area that had three sides to it, three walls, but it was an exterior space. We showed the production and thought it would make a great atrium with huge sweeping steps. It was an exterior you could shoot at night and turn into an interior, and you would hardly ever have to shoot off the walls."

Ma-Ma's machine gun onslaught.

Another signature Peach Trees sequence sees Ma-Ma's crew attempt to take out Dredd and Anderson half-way up the tower via machine guns, ripping apart one of the floors with a barrage of bullets. "We identified that as one of our hardest sequences to shoot," says Thum, so we previs'd that before we shot it. One of the reasons we used previs was that it was a big collaboration between departments - art department, sets, Max Poolman's special effects team and of course visual effects."

Prime Focus extended views of the Peach Trees interiors, augmented numerous practical wall and squib hits and added tracer fire for the gun fight. "For the tracers we looked at real footage," says Thum, "but we had to find the right place between them looking real and looking exciting. Sometimes they can just look a bit like Star Wars lasers. And then even though a real wall was destroyed, we still had to add some CG wall destruction, smoke, bullet hits, fire and interactive lighting with the tracers."

The science of Slo-Mo

In the Dredd world, Ma-Ma controls the manufacture and distribution of Slo-Mo, a new drug that gives users a sense of warped time. To depict the drug-taking graphically, DOP Anthony Dod Mantle relied on high-speed photography with Vision Research's Phantom Flex camera. "There was a bit of trepidation initially about how long can you hold on a slow-mo shot for," admits Thum. "Most films do the speed ramp thing in and out of the slow-mo to keep the energy going. We cut a lot of reels together and even did some slow-mo previs at one point to test it. Things that work well are water, smoke and fire and explosions. But also people's reactions work well - when people are punched in the face you just see the most crazy things happen to their face and so we thought, 'What if someone got shot in the face in slow-mo?'."


- Above: watch the Slo-Mo gunfight. Warning: some graphic violence.

That realization upped the intensity of the Slo-Mo scenes to views of bullets flying and direct body and face bullet hits. More tests were carried out with blood bags, prosthetics and shooting real bullets in slow motion. "The other idea we had was blowing compressed air at people," says Thum. "So for one shot where a guy's stomach ripples - that's all compressed air. For the guys being shot in the cheek we had something in their mouths and we were blowing compressed air at them, or sometimes they had squibs in the mouth. We'd get as much as possible of the real thing and sometimes the most interesting thing was the unexpected."

Part of the Slo-Mo sequence.

Visual effects artists then embellished the Slo-Mo shots with digital augmentations. Baseblack, in particular, was called upon to add practical and RealFlow blood and spit spurts, bullet trails and muzzle explosions for the shoot-up of Ma-Ma's men by Judge Dredd, even comp'ing in Nuke some blood spurts into floating windows for extra stereo impact. "The bullet coming out of the gun was an interesting shot," says Thum. "Baseblack did a few sims and then for the third one I said, 'That's it!'. It was only the third time they'd had a go at it and I thought it just worked. It was a bit like doing it for real."

The Slow-Mo sequences are also permeated by a technicolor/rainbow color scheme to highlight the effect of the drug. "Instead of just increasing saturation," says Thum, "we isolated all the colors and took them in different directions so it felt slightly unreal. Then we had the rainbow effect and took out the highlights and separated out the colors into a rainbow. It felt like going through a prism. We also added little sparkles to the highlights and make it feel otherworldly."

Watch a behind the scenes clip of the gunfight scene. Note: no sound in this clip.

Melting magic

In one startling sequence, Dredd fires a phosphorus bullet into the mouth of Zwirner (Jason Cope), igniting the character's face from the inside and causing it to melt. Visual effects were handled by The Mill under supervisor Sara Bennett. "They were going for a flare gun melting effect," says Bennett, "so we sat down and looked through a lot of film reference like Dead Calm and Raiders of the Lost Ark."

Head over to The Mill's website for a behind the scenes video on this shot.

The Mill previs'd the shots for timing before the scene was filmed. On set, photo reference was taken of Cope, whose character had complex facial tattoos and a lot of blood from the scene. A 3D scan was also undertaken. "Once we shot the scene we realized we'd have to do a full CG take-over at some point for full control," says Bennett. "So once we got the plates turned over we did a post-viz on the sequence, choreographed all the key stages before moving onto the final elements."

Dredd fires the phosphorous bullet.

Artists modeled the inside of Zwirner's head based on the 3D scan, building a skull, veins and fat muscles that would be revealed as the phosphorous bullet burned through. "For the melting effect we used Houdini," explains Bennett. "We developed a technique for propagating the attribute across geometry to represent the heat being emitted from the bullet. We scattered a lot of points over the head and then allowed the heat to increase in value over time, and then when it reached a point, that point was deleted - it was all meshed and gave the effect of holes growing across the surface."

"For the melting flesh," adds Bennett, "we used Houdini to do a high viscosity fluid simulation that allowed the face to melt down with the correct gravity. The rest was done in Maya and Mental Ray - we ended up with about 40 layers of CG, done in stereo. There was also a lot of FumeFX and 3ds Max work for smoke and sparks pouring out of his mouth too. It was great fun to work on!"

Dredd surveys the damage caused.

The melting head shots were complemented by The Mill's effects for Anderson's mind reading ability, depicted as a trail effect with color off-sets and a flickering distortion look. "It was done in 2D in Nuke," recounts Bennett. "We created a depth map within Nuke in 2D so in a wider room it started closer to Anderson and fell away from her. And because it was stereo it made it a bit more interesting."

Along with several gore enhancements and blood hits - incorporating practical effects and RealFlow sims - The Mill also completed a standalone effect of Anderson reading the mind of a man who has taken her hostage. Here, she sees the earlier live skinning by Ma-Ma's henchmen. "They gave us some stock footage of a farmer skinning an animal," says Bennett. "We did a matchmove on the skin and replaced it with a cloth solver in Maya to make it look like human skin. And again the guy had many tattoos as well so we took photos of him and projected that on top of the skin."

Artist Simon Bisley crafted this painting of The Mill's crew to celebrate the studio's work. Sara Bennett tells fxguide: "We commissioned Simon Bisley who is a renowned comic book artist for 2000 AD to paint up a picture of the team in a Dredd style, which we thought would be a fun thing to do."

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