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The CG animals that VFX Supervisor Christian Manz and his team at Framestore created for ‘Nanny McPhee and the Big Bang’ may not seem remarkable to look at – a perfectly realistic baby elephant, some piglets and a jackdaw. But their fantastic performances set them apart.From Digital Media World Magazine


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“We started working on Nanny McPhee early in 2009 and worked with the production VFX Supervisor, Adam McInnes, and the director, Susanna White, in pre-production,” said Christian. “They intended to shoot with real animals whose look and behaviour we'd have to match perfectly. When we first discussed approaches to the animals with Susanna White and her producers, they were adamant that the animals be photo-realistic, even after they came under the influence of Nanny McPhee's magic. These are emphatically not fantasy or cartoon animals or even performing animals, but simply ordinary creatures who find themselves suddenly able to do extraordinary things."

Nanny’s Menagerie
Because young elephant had to walk up stairs and get under the covers with the children, the pigs climbed trees and swam together in formation, and the jackdaw needed to act as Nanny McPhee’s faithful friend and henchman, the VFX team and animators had to be convinced that these stunts were achievable and have a clear plan of action.

“Framestore's Animation director, Michael Eames, led a series of animation tests as proof of concept for key scenes including the pigs’ synchronised swim and tree climb. These blew everybody away and gave the production confidence that what was being storyboarded would work in the context of the story,” Christian said.

“Once filming began I attended about 30 days of the shoot - we were there on days involving CG elements, to make sure all bases were covered. I also gave Adam support on days where VFX were split across units - as often happens - especially towards the end of the shoot. Our CG Supervisor Chris Lawrence attended on some days to make sure he was happy with the set-up. We also took VFX co-ordinators and tracking artists on some days to support the work being done by Adam's two on set data wranglers.”

Set Referencing
Producing photorealistic creatures who did extraordinary things required the capture of extensive on-set data. “We took a lot of photographic reference everyday on set. This took the form of 'tourist' photos of each set-up, texture references and HDR tiles to be used for reflection cards in the pond, for example. We also, of course, took HDR fisheyes of each set-up to use as environment and reflection maps when lighting the creatures and other CG assets. All the usual camera information was recorded and lighting balls filmed per set-up. “We also had a stereo SLR set up for photogrammetric reference of the pigs and other CG build items. These were utilised in Image Modeler to create calibrated scenes for the modelling artists. All data was downloaded every day and catalogued by the on-set data wranglers, who then passed it on to us for our use.”

A photographic reference shoot was done for the elephant, pigs and bird, and they also shot video reference for the animators of all the creatures. The swimming pigs sequence was complicated by the fact that the animation had to be finalised at an early stage, because the water interaction and water effects had to be customised to fit it, and there would be no chance after that for further adjustment. Consequently, several days of element shoots towards the end of the filming schedule included water splashes and interaction for this sequence, as well as blowing barley for the climactic scene and various incidental FX. There was also a bluescreen shoot for the vehicles and people who would populate the London sequence.

Absolutely Real
“The brief we had for the creatures was that they should be absolutely photo-real,” said Christian. “There was no design element - a pig had to look like a pig! Both the photographic and video reference we took was studied in detail by the Animation Supervisor Kevin Spruce, Chris Lawrence and also the rigging and modelling team to determine the key attributes required for performance and look. The rigs were based on skeleton reference – indeed, a skeleton model was used as a blocker in our lighting model to create realistic subsurface scattering.
Initially, a real baby elephant was trained to work with actress Emma Thompson, which didn’t work out in the end but provided excellent reference for the creation of a full CG elephant. He appears in a couple of sequences inside the farmhouse and barn, a ‘vision’ seen only by Nanny. It was a small part but, for the team, the mechanics involved in walking an elephant convincingly upstairs and into bed were complex.

“We do our modelling in Maya with extra detail sculpted in Mudbox. Rigging is based in Maya also, where we use a range of custom tools and deformers. Our R&D team did a lot of work to enhance our feather system - resulting in quick render times which were essential for the short schedule of the show.

Wing Anatomy
“While the pig and elephant were more 'standard' creatures, the jackdaw was more of a challenge. We studied the wing anatomy in great detail - even purchasing a taxidermied bird to aid this process. How a wing folds, and preserves volume as it does so, was the main headache that the team of riggers had to solve. Once feathered with our proprietary feather system, lit and comped, the resulting bird was hard to spot in among shots of the real thing.”

The animals were completely CG. There was no blending or muzzle replacement, for example. “However, especially in the case of the jackdaw, our CG creations were often intercut with the real thing. This was one of biggest challenges of the show - the match in look and performance had to be perfect.” Altogether, creating the 50 or so CG jackdaw shots - encompassing R&D, rigging, grooming and animation - took six months intensive work.

Animator-VFX Collaboration
They light and surface CG characters with in-house software, which is an interface between Maya and Renderman. The lighters match the creatures to the plate using the references taken on set while also attending to the groom of any hair and feathers. The lighters work very closely with compositing in the look development process, as this is where the final colour balancing and so on is carried out. About 150 iterations of look development were done for each creature asset - always referencing the real thing. Interactions in the form of physical elements and shadows add to the feeling that the creature is in the plate.

Because Framestore has a long history creature animation and VFX work, the animators are part of the VFX team. “The Animation Supervisor - in this case Kevin Spruce - collaborates closely with the CG Supervisor and myself as VFX Supervisor. The tools and workflow we have in place allow for the best possible finish to a shot in terms of VFX without compromising animation performance,” Christian explained. “Once animation is complete the creatures are passed on to our creature FX department who simulate effects like skin slide and fat jiggle onto the high resolution meshes. This adds weight and final finish to the animation.”

Wet Pigs
During the animation tests carried out in pre-production, they tried out several approaches to the synchronized-swimming piglets, starting from what a pig could realistically do and progressing to a more anthropomorphic swimming style. What worked best was a happy medium between the two. “Making them swim completely like humans looked a little strange, as well as not truly matching the brief. Swimming like a small dog seemed to work a lot better and felt more like it could have been achieved with a real pig,” said Christian.

The critical water interaction with the pigs demanded both 2D and 3D water simulations. “We used Houdini on ‘Nanny’ but on other projects we have and are using our proprietary water tool via Maya and Renderman. Houdini suited both the task - and the fantastic FX artist who did the work. 3D simulations were used to create the volumetric interactions from the pigs as they swim around. Often there are problems in getting enough resolution into these sims to stand up to cinema resolution so 2D simulations for the pond surface such as ripples, were used to enhance the level of detail required. Multiple simulations could be combined to get the desired effect. Also, 2D sims are far quicker to process than 3D ones and therefore easier to tweak.”

Framestore also worked on effects for the first ‘Nanny McPhee’ movie, made in 2005, but unfortunately, there wasn't much they could use from the production. The main effect they had to recreate was Nanny's magical stick ‘bang’ which instigates the magical action in the film. They restored the final 2K VFX shots purely for reference, recreating the FX and comp setup to enhance and improve on the original.

Environmental Work
Apart from the farm’s menagerie, Framestore’s VFX team also got to work on the varied environments in the movie. The barley field seen at the Green’s farm was actually located 70km away from the farmhouse itself, which meant a digital field had to be added to some shots.
“The opening shot of the film was the most challenging in this respect - involving a large helicopter camera move that needed stabilising and tracking before our field could be added,” Christian said. “The barley field was created with a hair system utilising in-house tools for dynamics. In turn, some shots filmed in the real field required us to add a matte painted farmhouse in the background. In wide shots of the farm there was also extensive removal of contemporary artifacts such as power lines.”

A lot of wire and rig removal was called for in the climactic scene where the villainous Topsey and Turvey are sucked out of the farmhouse by the magical wind while cornering Uncle Phil. A combination of bluescreen and in set wire work required extensive clean up and retiming.

Trip to London
Framestore’s matte painting team worked mainly on the London sequence, in which Nanny and the two boys travel though wartime London by motorbike, and which also needed a number of set extensions. They were handed pictorial research done by the production designer and did some of their own to help fulfill the director's brief. Plates were shot at the locations involved - Buckingham Palace, Albert Bridge and Trafalgar Square - very early on Sunday mornings the previous summer to avoid the crowds and traffic associated with filming in the capital.

“All of these plates needed extensive paint-out and manipulation to remove modern day buildings and even to add period detail back in. The most involved of these was the shot of Battersea Power Station with Albert Bridge in the foreground,” said Christian. “In reality, Albert Bridge is about a mile up river from the power station, so these needed stitching together and the building itself needed a lot of digital repair. It has been in ruins for decades. All these locations were local to our offices so our Matte Painting Supervisor Jason Horley was able to get his own photographic reference, as well as using our extensive reference library of period images. “Matte painting work was carried out in Photoshop and composited in Nuke, used for about 90 per cent of the comp work on the show. Nuke's ability to share assets with 3D such as cameras and models was invaluable.”

Classic Cars
To maintain the wartime setting of the film, the team built several CG period vehicles - cars, taxis and buses - based on vehicles sourced for the production by the art department. They had access to them during the production for reference photography and recording physical measurements. Photogrammetry was used in combination with Image Modeller to create calibrated scenes which the CG artists could use to build the finished assets.

Although there was several days of element photography involving the practical vehicles and people being shot to match specific plates, those seen in the VFX shots ended up being mostly CG. This was due to changes in both camera angles and lighting in post, where the use of the cg vehicles became the only way to achieve the finished shots. We also modelled a set of digital doubles based upon reference extras from the element shoot. These were used to populate both the background of our shots as well as the vehicles themselves.

Moving Statues
If you keep your eyes open as Nanny and the children motor through London, you’ll notice that some of the statues spring to life for a moment, such as a lion in Trafalgar Square and Nelson’s column. “There was much discussion in preproduction of how to achieve the animated statues. The lion was always slated to be CG but different methodologies were considered for Nelson, from CG to what was eventually shot - an actor in costume.

Toby Sedgewick, the films' movement director, was dressed in a prosthetic costume and mask crafted by the film’s make-up designer Peter King. He was shot against a bluescreen and comped into the finished shots. We made a simple model of him that was matte painted and projected as 2 1/2D in Nuke in wider shots where a new camera move was desired.

The lion was, again, modelled based on photogrammetric reference that we shot in Trafalgar Square. A lot work went into how he was rigged to move - too much stretching would make him look like rubber rather than cast iron. The finished shot was based on a filmed plate where the real lion and background were removed. We also filmed some bluescreen pigeons on one of the element shoots that, once comped in, created some interaction with our CG statue for realism.

 

Magic Wind
The film's climactic VFX sequence takes place in the barley field, with Nanny McPhee standing in its centre magically guiding the vital harvest of barley up into the air, where it moves like a flock of birds coalescing into series of animal and other shapes before blowing out and pouring back down to the field. CG Supervisor Chris Lawrence and a team of six created the wind as an animation-driven flocking simulation within Houdini.

Chris explained that the story demanded an animation-centric approach for this sequence. “From the outset we discussed this approach with director Susanna White. The idea was to get a very directed scene that conveyed a sense of awe and wonder at the magical animal forms. This also tied in with what was always an incredibly short schedule for the work - normally we would have wanted twice as long to complete a job like this, involving several minutes of animation and simulation.

“We started off rigging a bunch of assets in Maya to block the scene out, then we encouraged our animators Craig Bardsley and Craig Penn to go 'off piste' and really push things around, breaking rigs until they were happy with silhouette and form. They happily obliged and we took the result into Houdini, where Carlo Volpati and Michele Fabbro ran flocking simulations to instance particles of barley. It was a true meeting of disciplines - they did a great job of bringing the animated barley characters to life.

In the meantime, the twister and 'harvester' simulation was developed by Michele, Alvin Yap and Jacob Clark in Houdini, while Joe Gaffney did the barley field itself in Maya using proprietary hair tools. All of this work was composited by a team in Nuke where various finishing touches were applied.

“We had considered a few options before settling on the final approach - Houdini won out for the simulation work because it is so versatile and we have a great Houdini crew. It made more sense to use our proprietary 'fHairFilters' system to do the field simulations as it could better cope with the number of hairs - I believe there were over 10 million barley stalks in some of the wider shots.

Words: Adriene Hurst
Images: Universal Pictures and Framestore CFC
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