At first glance, this Liberty Group Limited spot showcasing Sandton City in South Africa is a clever 40 year reverse timelapse. But behind the scenes are a whole bunch of innovative visual effects techniques from Digital Domain, including photogrammetric reconstructions of the environment, testing a shoot with apple boxes, digital tree and environment generation and the grunt work of delicate hand animation. We talk to visual effects supervisor James Atkinson about how DD made the spot – known as ‘Answer’ – possible. And we feature an exclusive making of video.
‘Answer’ tells the story of how Sandton City, a high-end shopping and office complex near Johannesburg, rose up from being a farmers field to become ‘the richest square mile in Africa’. To do that, agency FoxP2 Johannesburg, production company Velocity Films and director Adrian De Sa Garces had DD imagine the scene as a CG walkbalk through time – from 2013 to 1973 – from the bustling commercial center, through its construction and to the field itself at the earliest stages of Sandton City’s planning.
Apple boxes and photogrammetry
If the Sandton City area was being re-created for a high-budget feature film, it would perhaps have been a candidate for days, if not weeks, of surveying, LIDAR scanning and photographic reference. But, ‘Answer’ had to be completed on a TVC budget and schedule of nine weeks. There were other challenges too. The area to be re-created in CG – 18 buildings plus a large mall – was close to a square kilometer with the original buildings designed in a pre-CAD era. One solution considered was scouring Google Maps and Street View imagery for reference, but since the Sandton City buildings were so new, the Google images were only construction pits.
Ultimately, Atkinson took a photogrammetric approach with Agisoft’s PhotoScan tool that began in Digital Domain’s car park. “We built a miniature city out of apple boxes in the DD parking lot and walked around it with a still camera, pretending we were a helicopter, then fed the photos into Agisoft,” explains Atkinson. “Once we found the right combination of lens and camera path, we arranged for a helicopter flight during the Johannesburg shoot.”
Atkinson then photographed the actual Sandton City city from the chopper with a Canon 5D from 300 meters above the zone using a variety of lenses. “I was able to send that photo shoot back to the integration team at Digital Domain,” he says, “and then we used Agisoft to build a pretty damn good proxy of the site. If you cross-dissolve between the actual Agisoft survey and the result, it’s very close. The only differences are intentional to give nicer silhouettes of the buildings.”
Making it move
Using the proxy as a measurement guide, DD made deconstructible models of each building that included an internal construction prop kit. The studio’s toolkit was mostly a Maya to V-Ray pipe. “The prop kit consisted of dozens of unique models,” notes Atkinson, “many of which had internal animation. We were able to create a few rigging tools to assist with decimation and time-lapse animation – where everything is on a step-curve – but most of the animation ended up being created the old-fashioned way, with manual keys.”
V-Ray proxies were relied on as animation progressed, since, as Atkinson explains “there were many thousands of models in each layer and little time for optimization. Normally in a continuous camera spot, you can build in cut points such as flying through clouds or wiping the frame with foreground objects. This spot provided only one such point (the tree), but even then we had to see the background evolve, so the choreography proved to be quite tricky. Fortunately, we had Scott Meadows, DD’s Previs Supervisor, on the job for animation, and the entire crew pitched in to saturate the sequence with animated micro-details.”
The ‘twitching’ cars were especially challenging and also ended up being mostly hand-animated rather than via a procedural approach. Says Atkinson: “Due to the short schedule of nine weeks and sheer volume of animation, we found that, with the exception of a few deformation and curve editing tools that let us set step frames (for smooth interpolation) a lot of what we created was hand animated. We had a script to assist with the cars with randomizing their layouts, but because they had to be in actual parking spots which were on the rooftop, and not running over pedestrians, a lot had to be animated by hand.”
Although keyframed animation was the major approach, in order to help depict the (de)constructing of the buildings, DD used what they called a ‘Pacman-rig tool’ which allowed artists to animate boxes flying over buildings and permanently decimate anything that the Pacman box touched.
Selling the reverse timelapse look
“Rather than mimic pure timelapse where lighting and weather can change dramatically from frame-to-frame,” outlines Atkinson, “our director wanted the spot to have a smooth evolution through two day/night cycles and four seasons. We looked at lots of time lapse, like One World Trade Center being built or other construction sites, and depending on how long the interval is – obviously the longer the interval, the bigger the changes in weather, lighting, time of day – it can have massive stroboscopic effects and he wanted to avoid that.”
For DD, that meant that having a convincing cloud and weather ‘movement’ through the spot was crucial. “Our CG Supervisor, Greg Teegarden, built a time-lapsing sky in Terragen,” says Atkinson, “and one of the coolest features was the ability to render an HDR of the same sequence, which was used to light the V-Ray buildings, so lighting integration was a snap. You get some terrific scattering and color temperature effects in Terragen, especially at magic hour, so we cheated the sun to rush through night and mid-day, but hang out longer during sunrise and sunset.”
The timelapse look had to be applied to the tree – a digital creation – too. “The reverse-growing tree provided a unique opportunity to deploy some cool new features in SpeedTree,” comments Atkinson. “The developers at IDV provided us with a beta version for animated growth, and worked closely with us to add the controls needed to massage timing on individual branches and leaves. The resulting animated asset was one of our most complex, with a 55 gigabyte Alembic file generated on each version.”
Interestingly, the timelapse animation was implemented for both a 60 second final and a 45 second cut-down of the spot. Usually, a cut-down of a continuous shot can prove difficult because the timing is locked in and therefore requires re-animation. But, as Atkinson explains, DD was able to drop frames and still make the 45 second version work. “By selectively dropping frames in portions of the shot, it actually enhanced the timelapse look. We simply elapsed more time. It ended up being one of the friendliest cut-down spots we’ve ever done. In many ways it looked better. We did do some selective optical flow blending for portions of the frame. The frame dropping proved to be a nice complement to the stochastic animation.”
CG meets live action
Once the camera passes by the tree, the spot merges into a live action plate of three actors on the site of Sandton City in 1973. “We shot the end plate on a farm outside of Johannesburg,” says Atkinson, with the crane shot matching a previs of the move from lens, camera height and crane position information. Ultimately, the final shot was almost completely rebuilt in Nuke to match a historical photo of the original site that had been provided to DD. “The only practical portion remaining was a patch of grass with our three guys and their car; the rest was replaced with matte paintings and CG trees.”
Certainly, ‘Answer’ is a TVC that should be watched and re-watched. “The devil is in the details,” suggests Atkinson. “That was the mantra for this spot. Once you start adding people, for example, then you have to start adding variations of people, and then you have to start adding people pushing shopping trolleys and clusters in different outfits. It was very iterative, like painting detail in the corner of a picture demands other details to be painted around it. It was a very organic process of things being built up.”
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