In Oz the Great and Powerful, Sony Pictures Imageworks conjures a CGI vision of an iconic fantasy world. James Clarke discovers the magic behind the effects
The entertainment industry has been adapting and creatively mining L Frank Baum’s Oz books ever since a 1901 Broadway musical. The latest movie version, Oz The Great and Powerful, directed by fantasy-film veteran Sam Raimi, explores the origins of the enigmatic wizard from Baum’s original novel, The Wonderful Wizard of Oz. Sam Raimi’s prequel plays to his strengths as a director, with Oz portrayed as a rich, imaginary world that’s both bright and dark, full of fantastical characters and exciting events.
To help create this immersive world, Raimi brought in two-time Oscar winner Robert Stromberg, the production designer behind Avatar and Alice in Wonderland. Instead of relying on greenscreen technology for every scene, they decided to construct physical sets so the actors could have a visual reference. “Robert worked with artists to build things on set very early on as an art-directed stage aesthetic,” says visual effects supervisor Scott Stokdyk, who has worked with Raimi on several projects – most notably the Spider-Man trilogy, sharing an Oscar for his work on the second in the series.
To build the digital versions of all the locations and lands in the movie, the visual effects team had laser-scanned versions of the physical sets. For example, in the scene where Oz first sees the Yellow Brick Road in the company of the witch Theodora, the team scanned the environment and modified it. “The topography gives us great visual cues, which we cherry-pick and re-art direct,” says Stokdyk. The team accumulated digital assets, such as greenery, and then were able to re-dress the set digitally.
“It is harder to combine live-action and CG, but we resisted the trend to go all-CG,” says animation supervisor Troy Saliba. In all there were 1,105 shots, and Raimi demanded only the best for each. “One of the things I love about working with Sam Raimi is that he keeps you on your toes,” says Stokdyk. “He was constantly challenging us to incorporate everything he wanted, and to create a consistent tone.”
THE LANDS OF OZ
Principal photography on Oz The Great and Powerful took place in Detroit, Michigan in the second half of 2011. During this phase, Sony Pictures Imageworks gathered information and data on-set to eventually refer to in post-production, which ran for a year from January 2012.
The visual effects team laser-scanned the physical sets in order to build the digital versions of all the locations
Balancing the on-set lighting with CG lighting was an overall aesthetic goal for the movie. In collaboration with Peter Deming, the film’s director of photography, the team gathered all the necessary data for the CG lighting in post. Sony Pictures Imageworks used a Spheron HDR camera to gather its extensive library of 360-degree photographs of the set; from these they made detailed records of on-set light positions and light intensity values to translate into the CG realm.
As well as building the surreal world, the team was tasked with creating digital characters and landscapes, such as a city of teapots. “We were doing flying monkeys and bubbles flying through beautiful landscapes,” says Stokdyk. The team used the original books for reference to the surreal world, and took visual cues from the original illustrations by WW Denslow for the fantastic characters.
Stokdyk admits that they didn’t even scratch the surface in terms of creatures they could have featured. One wonderful character they decided to bring to the big screen was China Girl, but creating her was fraught with technical difficulties.
A SMASHING LITTLE DOLL
China Girl presented a unique animation challenge. After seeing the first pieces of animation for the character, animation supervisor Troy Saliba recalls how he had to tell a rather surprised animator that the animation was too articulated, and that it had to be dialled back in its expressivity, which is rather counterintuitive. Saliba explained how the creative trick with China Girl was in capturing “a childish preciousness in a little porcelain doll, with her face all one piece”. They had to address the character’s movement, but also how to best make her face move without drawing the audience away from the illusion that she was made of china. “Because of the limitations, China Girl is really unique – there’s no recognisable animation formula for her,” Saliba explains.
Animating her was not only technically challenging, but also extremely time-consuming. For a ten-second shot, such as the one of China Girl interacting with Oscar Diggs (played by James Franco), the crew would typically commit ten to 12 hours per day over four weeks to the process of solving the dynamics of movement. With work on this part of the character animation completed, animation would then be produced for the cloth simulation and the interaction of the characters.
The animators were asked to ‘dial back‘ the expressiveness of China Doll’s face to keep the illusion that she was made of china
To keep the interaction of the digital and live characters believable, Stokdyk devised the Puppetcam, a pole attached to a marionette that allowed the actors on the set to see the face of the voice actor. “Puppetcam really helped with ad-libbing and vital performance,” says Saliba. Unfortunately, China Girl was too small to use the ingenious Puppetcam, and so a marionette was used on the set, operated by talented manipulator Phillip Huber.
Getting eye levels was just one of the issues. Saliba recalls how the film’s animated character work also included significant efforts to generate a wide range of digital doubles for the human characters. Additionally, thousands of digi-doubles were generated as extras to populate the land of Oz. “The toughest ones were stunt doubles for hero characters, because they were closer to the camera than we expected,” says Saliba. The team found creating digi-doubles of the witches particularly troublesome, because they had to try to capture the attitude of each witch when they were in flight around Oz.
“For the 3D characters, we were infusing a bit of the actor into the performance,” says Saliba. “Once we have a model, we start rigging and doing the facial poses. There’s some back and forth on modelling, depending on the topology of the face.” Animation tests of each character were produced once the rigging was developed, which would then go to Raimi for approval.
STEREOSCOPIC MAGIC
By January 2012, edits of live-action footage began reaching Sony Pictures Imageworks. Simultaneously, work began on some of the film’s more complex digital environments. It was an evolving process, and part of this creative evolution was in terms of the film’s 3D demands. Scott Willman, the film’s stereography supervisor, came on board immediately after the principal photography was complete, for which the on-set 3D stereographers had been Ed Marsh and James Goldman. One of Wilman’s key responsibilities was to oversee how animated characters would tie in with the movie’s 3D aesthetic. Willman recalls that Raimi’s feedback upon reviewing the 3D footage was to “make it bigger”.
FLEXIBLE DESIGN DEPTH
Oz The Great and Powerful had always been intended as a stereoscopic film, and so it had been shot natively in 3D rather than being converted to 3D in post-production. As such, the stereo element of the film was essentially set in stone by the time the footage from principal photography reached Sony Pictures Imageworks.
Willman explains that across the film there was lots of flexibility to design depth, making sure that multiple camera depths still worked with the native photography.
“Shooting native on-set was James Goldman, and it was his call to set the interaxial for the on-set camera. We’re used to seeing everything in binocular, and it’s important that things have a basis in reality, so in matchmoving we make sure that the CG has the same distance from the camera as the live action. There’s a higher degree of fidelity in stereo,” he says.
The film was shot natively in stereoscopic 3D rather than being converted to 3D in post-production
The Sony Pictures Imageworks team was able to enhance the native footage with new visual effects elements and stereoscopic adjustments. Being able to direct various aesthetic choices after principal photography was a great boon.
As the crew grappled with the climax of the film, they went back to the source material. “There’s a big effects sequence at the end of the film with a giant projected holographic head,” explains Stokdyk. “We wanted it to be an original-looking creation, so we looked back at the books – and there’s a floating head over a throne graphic. That’s what we went with.”
So, in a bright new digital world the old-world inspiration endures, and as the animators and visual effects crew become more comfortable with the technology, so their creative choices expand and unfold like a Yellow Brick Road.
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