Stereo Twice Over
Issue: Volume: 32 Issue: 10 (Oct. 2009)

Stereo Twice Over

Fourteen years ago, Pixar Animation Studios released Toy Story, the first feature film created with 3D computer graphics. This year, that film and its sequel, Toy Story 2, become Disney/Pixar’s second and third features to receive the full 3D treatment—stereo 3D. Up was the first. Bob Whitehill, lead stereographer, supervised the stereo work for all three.

Woody and Buzz, the first CG characters to star in an animated feature, step into the future in Pixar’s stereo 3D versions of the much-loved films.
Take a nostalgic look back in time at how Pixar created the original Toy Story and Toy Story 2.

“We went back and forth with John Lasseter until we found our footing,” Whitehill says. “Creatively, we needed to find a template for how to use 3D in the studio, the range we wanted to use. I call it the three Cs: comfortable, consistent with what the original film had in mind, and captivating. We want it to be immersive, to draw you into the story. At no time is our goal to make 3D a reason to bring people into the theater.”

Comfort is rule number one for most stereographers, who, like Whitehill, make sure left- and right-eye images match. “Color disparity is bad, but the worst is vertical disparity,” he says, “when one image is higher than the other. Moving the scenes in Z depth can also cause eyestrain. We think about how far out and how deep to make the scenes.”

The distance the toys must travel to cross the street stretches way back in stereo 3D. To enhance the story, lead stereographer Bob Whitehill increased depth when the toys are in the human world.
To Whitehill, that means keep it simple. He begins by setting the screen depth at the point of interest. In other words, the 3D scene could extend entirely back from the theater screen, zoom completely out in the front, or be somewhere in the middle. Whitehill puts the characters or the area in a scene that the directors want you to focus on at the screen, and, by angling the left and right cameras, sets the point of convergence for your eyes at that depth. If you focus on an index finger held in front of your eyes, you can see how convergence works.

“That’s one of our main 3D philosophies,” Whitehill says, “the idea that you can keep your point of interest at screen depth and then accordion around it. It’s like watching a 2D movie with added depth around the point of focus.

“Some studios bring the focus out into audience space thinking you’ll feel the depth more,” Whitehill adds. “People do like the roller-coaster films, and God bless them. But, we want stereo 3D to be a window into a new world, not draw attention to itself. People go to movies to get lost in the movie.”

To help keep people comfortable while watching a film in stereo, Whitehill manipulates convergence and interocular distance between shots so the audience doesn’t need to refocus. Inter­ocular refers to the distance between our eyes, or, in stereo 3D, the distance between two cameras. This separation between cameras determines how far a scene stretches in 3D space and gives individual objects in the scene three dimensionality, that is, roundness—especially those closest to the camera. Some studios tinker with that effect by assigning individual cameras to specific elements, or perhaps split scenes into foreground, mid-ground, and background elements, each with its own set of cameras, to put round characters deeper into the scene. 

“I stay away from assigning interocular distance to different elements within a shot and from animating interocular distance within a shot,” Whitehill says. “We change the interocular on a shot-by-shot basis to create the depths we want, but the farther apart the lenses get, the more you risk miniaturizing the scene. If you separate the cameras too much, your right eye might see one ear on a character and your left eye would see the other ear, so your brain miniaturizes the character and it becomes a doll. You have to be careful. We err on the side of comfort to make the stereo true to the experience you expect.”

Usually, the audience watches the film as if they are looking through a window, which is similar to the way Whitehill used stereo for Up, but not always. “In a lot of the compositions, we inherited elements that come forward,” Whitehill says. “For example, the camera might be low on the ground with Woody standing a little ways away. When we put him right at the screen, the ground plane comes forward and whatever is behind him goes back.
Whitehill’s second stereography rule, consistency, meant that the 3D version had to support the original film. So, when he considered re-rendering Toy Story and Toy Story 2 in stereo 3D, he looked for ways to enhance the story. “We concentrated on two aspects,” Whitehill says, “the environment and emotional content.”

Pixar didn’t simply convert the films to stereo 3D; the studio re-rendered every frame to create the left and right eye, which meant resurrecting 14-year-old files and code created on 1995 workstations.
When scenes take place in the toy world, Whitehill reduced the depth to make the environment understandable and consistent with the toys’ size. But, when humans entered the world, he increased the depth. “I wanted to make the human world overwhelming,” he says. “As if the world is stacked against the toys.”

In terms of emotional content, Whitehill used stereo to support two overall themes: connection and alienation. When Woody is comfortable and connected to the characters around him, Whitehill reduced the stereo 3D effect. When Woody is emotionally alienated from the other toys, he increased the depth of the scenes around the detached character.

“There’s a scene between Woody and Buzz where Woody tells Buzz that being a toy is important,” Whitehill says. “I dialed down the 3D to have that moment of connection. Then, for the big rescue at the end, I go deep because [Woody and Buzz] are lost in the human world and separated from the other toys.”

As the stereo team worked, it discovered that the original films readily lent themselves to stereo 3D. “Toy Story was the first animated feature, so John [Lasseter] and the team recognized they had the ability to move the camera and the characters forward and back in space. So they did that repeatedly. It’s almost as though the films were conceived as stereo 3D movies, but they just weren’t able to project them that way.”

This rule, which embraces immersion and draws people into the story, seems almost like a subset, or maybe a superset, of the previous rule. But, it offers a chance to have Whitehill describe some of his favorite scenes in stereo and the fun he and the team must have had working with the classic films. “We didn’t want to distract from the story, but we wanted to give the audience a new experience and dimensionality,” he says. “We wanted to make it novel for them.”

The first that comes to mind is the climactic rocket ride, a stunning scene with the wonderful line, “This isn’t flying, it’s falling with style.” “You feel you can reach out and touch Woody and Buzz,” Whitehill says.

In Toy Story 2, Whitehill likes the elevator shaft sequence. “It makes for such great vanishing points as you look up or down,” he says. “And Zurg falling down into the darkness is a great 3D moment.”
Another favorite is the luggage conveyor belt at the airport. “The rubber curtain lifts to reveal a huge space with characters running along all these belts,” Whitehill says.

In the toy store, when tour guide Barbie knocks loose a pile of super balls, they bounce in 3D space in a way they never did on the flat screen.

“Oh, and when the toys cross the road,” Whitehill adds. “And I almost forgot, the opening sequence with Buzz playing the video game with Zurg. These are such charming and fun stories. They really work well in stereo.”

Making It All Work
Because Pixar created this film for flat screens, some shots had little cheats that the stereo crew needed to fix—eye lines that didn’t match directly but weren’t noticeable on the flat screen, paint fixes that landed in front of an object when seen in 3D, and intersections hidden in the 2D images. “A character’s finger might have brushed through a bedspread,” Whitehill says. “We had a few little things like that. But we didn’t change the composition or animation.”

The depth was dialed down for scenes in the toys’ world and for intimate moments between Buzz and Woody.
When scenes had background paintings, the stereo crew would separate the elements to give the backgrounds more depth. The scene in which Woody throws Christmas lights out of Sid’s window, hoping he can crawl down them, required the most layering. “That entire shot down the driveway of Andy’s house was a painting, other than the characters and animation, so we spent a lot of time layering and cutting elements out to make sure it felt true and right,” says Whitehill. “It was only two shots, but it was a lot of work.”

Whitehill worked with a proprietary system that he calls “results driven” to set the cameras. “It’s a really cool system,” he says. “I’m able to establish a plane and dial in the separation between the left and right eyes at that point in space.”

To describe how it works, Whitehill uses the example of someone pointing a stick toward the audience. “I can put a plane in front of the stick and another at the back, and then I can dial in the pixel separation as much as I want,” he says. “A separation of 20 pixels on a big screen would be dramatic.”

To make all this possible, the crew had to resurrect the original digital files. “We wanted to render the left and right eyes from the original renders,” Whitehill says. “We didn’t want to do a conversion.”

Some of the people who had worked on the original Toy Story helped extract the code from the old Silicon Graphics Octane machines and move it into the current pipeline. “Bill Reeves was instrumental, Bena Currin and Darwin Peachy were helpful, too,” Whitehill says. “It was a great challenge, but we overcame it.”

Despite 14 years of advancements in computer graphics, the original film still took the crew to infinity and beyond.

“We were all so impressed with how well it held up when we dived back into that environment,” Whitehill says. “We all fell in love with not only the look, which was so sophisticated for its time, but the characters, the dialog, and the humor. And, it maintained consistency. You could argue that Toy Story is the reason CG animated features exist in this industry. It’s certainly what attracted me to the industry. To be able to come to Pixar and live in the world of these characters has been such a joy for me.”