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September 2014
Issue: March 1, 2013

VFX: 'Oz the Great and Powerful'

By: Marc Loftus
CULVER CITY — Sony Pictures Imageworks contributed more than 1,100 shots to the new Disney film, Oz The Great and Powerful, which hit theatres on March 8. The film was shot natively in 3D and called on the Imageworks team to help director Sam Raimi achieve his stylized vision of the Land of Oz and its magical characters. 

The feature, which was shot using Red Epic cameras, centers around Oscar Diggs, a magician from Kansas (played by James Franco), who is transported to the magical land, where he encounters three witches — Theodora (Mika Kunis), Evanora (Rachel Weisz), and Glinda (Michelle Williams) — as well as the problems facing the great land. He also encounters the tiny China Girl (voiced by Joey King) and Finley (Zach Braff), the flying monkey.

Here, the film’s visual effects supervisor Scott Stokdyk (Oscar -Spider-Man 2) details the production process, the challenges and creating digital backgrounds and characters, and his work with director Sam Raimi.

Post: For a VFX heavy film like Oz the Great and Powerful, is it easier to describe what isn’t a visual effect?

Scott Stokdyk: “We started very early on thinking about that question: ‘What can we get in camera and what do we not have to do as visual effects?’ We decided to have everything shot on sound soundstages, but not in a style as much like Alice in Wonderland, where it was just actors over a sea of greenscreen. I did work on Alice and it’s part of the DNA at Imageworks here. They had two stages in Culver City, where as Oz had seven or eight large stages in Detroit. We filled the stages, wall to wall, with as much as real set build as we could, and with as many actors and extras, and as much set design that we could actually fit on the stage.

“We always tried to keep an openness to the set, where one or two sides have wide open areas of bluescreen for depth. We definitely designed and conceived it as a 3D movie, so we were always thinking in terms of volume and space.”

Post: How were the different stages set up?

Stokdyk: “It was incredible complicated how they switched around. There were larger and smaller sets, and the larger sets were more stable. Like Glida’s courtyard and the canvas circus stage. Some of the smaller stages they built and broke down. And what drove the stage layout and rotation was the stunt work. I worked with Scott Rogers, who was the stunt coordinator, on Spider-Man 3. And he drives all the wire work with high-speed wenches and computer control. It’s almost like motion control for the actor. He said we did more stunt work on Oz than on Spider-Man 3!”

Post: How important was previs?

Stokdyk: “It was absolutely driven by previs and tech vis. At the same time we were flying the actors, we are flying the cameras as well.

“A perfect example for previs is this bubble boy we have. The idea is that we wanted to fly the real actors and not always have them be CG. How can we do that? If in the previs they are flying at 100 miles per hour and travelling 500 feet, they won’t fit on the stage. We have to back out the camera relative to them and figure it out and how to cheat it.”

Post: Red Epics were used for the stereo shoot?

Stokdyk: “I would say 99 percent of the time we went with our standard rig, which was a 3D Element Technica Atom rig carrying two Red Epics. It was a mirror set-up and we had an incredible about of luck with it. For the most part, it was because we were in such a controlled stage environment. We got really excellent 3D stereography.”

Post: And the rig was used for the motion shots?

Stokdyk: “The rig was compact enough and lightweight enough that we were able to fly on cables and put it on a Technocrane and on dollies. It pretty much served almost every purpose. There were a couple of minor exceptions: There was one shot where we were flying the camera on a rail towards one of the evil witches at the end, right towards her face, and for stabilization issues went with a single Epic. I could probably count on one hand the number of shots where we had to go down to a single camera. It was very few.”

Post: Did Imageworks do the previs?

Stokdyk: “No, The Third Floor did previs and the post vis.”

Post: On-set, was production able to see how the elements would come together?

Stokdyk: “We used Joe Lewis’s EncodaCam system for virtual background replacement. I have worked with Joe Lewis over the years and really like working with him and his team. His system goes back to the iRobot days, the early 2000s, and it’s a pretty robust, well-established, production-ready system.

“More recently, the trend has been toward motion capture driven ways of virtual production. You motion capture the camera and then and apply and render your virtual background. But for our set-up, with the amount of stages we had, it was not practical to do that. I’ve always been really happy with the way Joe Lewis was able to encode the Technocranes, and the camera heads get really robust data with low overheard and the correct set up. In terms of the backgrounds, that’s what we did. And that’s been useful in terms of many shows, [where you’re] not just looking into a sea of blue, but visualizing what is back there.”

Post: There are a number of CG characters in the film?

Stokdyk: “We have two main characters: the China Girl and the talking monkey, and we treated them slightly differently. For China Girl, on-set we had a marionette that was 18-inches tall. Phillip Huber, the master marionette artist, built his own version of China Girl. So we would have James Franco talking to the marionette. We’d have great lighting reference and interaction with James. We would also have a rough animation guide of different motions, and a style and feel. Part B of that, we had the actress Joey King in a sound-proofed booth, off set, and she had a video monitor where she could seeing the A camera. And there was a camera on her, where we were recording performance and passing that to set. Audio-wise, she could hear James and talk to him.”

Post: The marionette would ultimately be replaced

Stokdyk: The Marionette gave us a bunch of things, but ultimately, it had to be replaced. We’d shoot clean plates. Troy Saliba and his animation team would base performance on a couple of things: anything interesting in the marionette’s performance, plus Joey’s performance in the booth, plus any other direction from Sam Raimi.”

Post: Tell us about Finley, the monkey?

Stokdyk: “Finley is the monkey who becomes Oz’s companion on the journey. He’s played by Zach Braff. The modern way for doing a CG character is to have them on-set, interacting actor to actor, and then paint out the stand-in actor and replace him with CG. We tried to do that whenever we could. But our CG Finley was three-feet-tall and had wings, could fly around, and was very active. So we couldn’t put Zach’s face where the monkey’s was. We came up with this thing called ‘puppet cam.’ We had a puppet with a rod, and a monitor and camera on the end of it. We had Zach in the same booth that Joey was in, and he was interacting. We set up a virtual video conference, but it was executed through a monitor on a stick on-set. James had an ear rig, and he could talk to Zach, but was looking at a video monitor on a stick, put in the place of where the monkey’s head would be. And in the monitor he’d see Zach’s head in the booth. It gave us a proxy for having Zack on-set with his head in the right place.”

Post: How does Sam Raimi approach visual effects?

Stokdyk: “Sam definitely comes from this background of pulling out whatever trick it takes to get the job done. He’s a very visual director and very interested in getting interesting things on-screen. He doesn’t necessarily care about the technique. Because he’s so visual, he likes seeing stuff, and sculpting it, and working with it, and that’s why it’s very easy for him to do that on-set. He likes to see as much as he can… but he’s not above, in post, replacing things he visualized on-set or reimagining things. He’s open to all these different techniques. 

“At one point there was a discussion about miniatures and if we could use miniatures on this movie? I felt pretty strongly that we shouldn’t use miniatures. I wanted it to be staged, directed, lit and composed — photography plus CG extensions, including CG matte paintings. I felt that going to miniatures would pop us into a different world, and [Sam] was fine with that. He’s done miniatures before and is open to them, and if I had said we really need to do miniatures here, he would have, but I don’t think that he lost any sleep over the fact that we didn’t do miniatures.

“He’s more about being able to tell a great visual story. He works extensively with previs and post vis to come up with those quirky ideas, but he doesn’t have too much worry about how you execute it. Sam is a very visual director, but he also cares and is so laser focused on performance and interaction between actors. In a way, I feel like he left a lot of the visual design to Robert Stromberg and myself. On-set, he was focused on working. He’s such a great actor’s director. And that’s one of the reasons this puppet cam set-up worked so well for him. He felt like it was a great tool for the actors and it wasn’t a gratuitous piece of technology.”

Post: What was Imageworks’ pipeline for this film?

Stokdyk: “The Imageworks pipeline has been mostly centered around Maya for a long, long time. It goes back to the Stuart Little days. Imageworks made a decision to be focused on character performance work, and felt they could build things into Maya. Over the past 10 to 15 years, all of these tools have evolved to be very character friendly.”

Post: What about visual effects?

Stokdyk: “A lot of the effects are done in Houdini, but our primary lighting and rendering package is a combination of Katana, for assembling everything together, and Arnold for rendering. Recently, we standardized on Nuke for compositing. I think Imageworks has a great relationship with The Foundry. It’s been really fantastic to solidify a pipeline with a couple of key software pieces. Maya is well established and really super reliable. Katana is extremely flexible and powerful for doing everything our lighters need to do. And then Nuke has become a compositing standard, I believe, and it’s so great to have artists come from other facilities that are really familiar with it. And Arnold is an incredibly-powerful renderer for getting a nice global illumination look and being able to work really well with our image-based lighting pipeline.”

Post: There are so many effects in this film. Are there any that stand out to you?

Stokdyk: “I went to the premiere and it was the first time I saw it all in context. I have two favorites. One is the bubble boy, because it was so intricate to shoot, and I think it turned out really beautiful with these bubbles floating through this exotic land.

“I would say my favorite is at the end, where these baboon creatures attack Glinda’s army that’s coming toward The Emerald City. We shot bits and pieces on-set as a guide, but ended up resculpting it for story points. How we revealed through lighting and composition, more and more to the audience… when I looked at it, it worked so well with sound and music. It’s a great combination of character animation and effects, because it’s got this magical fog that is woven into the character animation. And the lighting is so specific to what Sam’s needs were for the scene. It goes step by step in terms of showing a silhouette and then revealing a little bit of lighting on the edges, and then showing things backlit and silhouettes from another side, kind of flaring out. Shot by shot, we evolve the lighting and reveal more and more. I think it was a great artistic challenge as well as all of the technical stuff that’s all built into it.”