Sequels can be a little like high school reunions. You want to revisit old friends, but when you arrive, you realize you landed in some kind of alternate reality. The prom princess is now a tough cookie. The class clown turned into a donkey. The flirt got fat. From far, far away, high school may have seemed like a fairy tale. But, stuff happens.
So, too, with the characters in Shrek Forever After, the latest and last in a series of four animated features from PDI/DreamWorks that started with the Oscar-winning Shrek in 2001. In this film, all the familiar fairy-tale characters except Shrek change personality and sometimes size after he spins them into an alternate reality. The circus master for the wicked whirlwind is the devilish Rumpelstiltskin, who persuades our favorite green ogre to sign a magical contract. When Shrek does, the Kingdom of Far Far Away rips apart and reforms itself into a rougher, darker world.
The characters have the same voices—actors returning for the final Shrek chapter include Mike Myers (Shrek), Cameron Diaz (Princess Fiona), Antonio Banderas (Puss In Boots), Eddie Murphy (Donkey), and Julie Andrews (Queen Lillian). But, in the alternate world Shrek enters, every character we know has led a different, horrible life. Donkey doesn’t recognize Shrek and gallops away from him. Princess Fiona is still an ogre, but now she’s an athletic warrior who tosses her long hair in defiance; in this world, ogres are hated and hunted. Even the gingerbread cookie is a hardened gladiator. “Gingy is forced to fight animal crackers to the death,” says director Mike Mitchell. “It’s a violent scene. Crumbs fly everywhere.”
This is the first Shrek Mitchell has directed, though like many on the crew of approximately 500 artists, he has worked on previous Shrek films. “We held onto as many of the stars from previous films as we could, and we also injected a new energy by bringing in artists from Southpark and people I worked with on other jobs, like SpongeBob,” Mitchell says. “But, we made sure everyone was a gigantic Shrek fan. The challenge was that this sequel had to be as good as all the ones before, to be the best ever. And it’s in [stereo] 3D.”
Double the Trouble
Head of layout Yong Duk Jhun moved onto Shrek from Kung Fu Panda, where he had designed the stereo 3D sequence—the leopard Tylon’s escape—that helped persuade CEO Jeffrey Katzenberg to create all future animated films in stereo.
“I wasn’t a big fan of 3D a long time ago, but once I started working with stereo for Kung Fu Panda, I became one,” Jhun says. “For Shrek 4 [Forever After], we were in 3D right away, and it was a lot different. Traditionally in layout, we put in cameras and shoot actors. Now we’ve added another asset: depth. We made 3D a big part of the storytelling.”
Helping Jhun and the artists was a tool developed by Phil “Captain 3D” McNally called Happy Ratio, which gave them default settings for camera convergence and interocular distance. While the layout artists worked, they wore the polarized RealD glasses.
“We had a lot of discussion about whether to do a separate 2D version,” Jhun says. “We decided to make everything work in 3D, and for the 2D theaters, we would play only the left side of the camera.” The layout artists started with storyboards—pencil drawings in 2D from the story department that set the pace and the character’s emotional journey.
People are afraid of ogres in the alternate reality that Shrek entered after signing Rumpelstiltskin’s magic contract. Technical directors created many of these background characters by using the rig to sculpt variations of a generic model.
“We make the timing work in a real 3D space using real 3D assets,” Jhun explains. “For example, a storyboard character might walk from A to B in a few steps, but when we bring the character into the 3D set, the distance is farther so the character takes longer to walk.”
The layout artists also helped define the space by adding assets that transformed a simple 2D drawing that used layers of images into a more complex and deep stereo 3D scene. “In [stereo] 3D, if the set is too simple, the scene seems empty,” Jhun says. “So we’re forced to put more objects or assets into the scene to make it more interesting. But, we had to compose the scenes carefully so the audience wouldn’t be confused about where to look.” In addition, to help the audience know where to look, the layout artists sometimes used a slight depth of field.
As in any film, focusing the audience’s attention is important. In stereo 3D films, though, focus becomes a question of comfort as well as attention. Because people watching a stereo 3D film need time to adjust their eyes, the layout artists tried to compose shots that kept the same area of focus when the scene changed after a cut. When the shots were short, the artists might add extra frames. When that was impossible, they used a special blending technique.
“It’s very hard for an audience to adjust from far to close,” Jhun says. “In 2D, the audience doesn’t have to calculate the depth between an object and a character, but when you put depth into a scene, they do, and our brain takes a little longer to adjust. So, some shots got longer than they would have in regular 2D filmmaking. But, if that wasted storytelling time, we used something we called ‘blending.’ Even though an object is supposed to be far, we bring it closer and then let it slowly go deep, and the audience should not realize what we’re doing.”
The layout artists also used this ability to move characters subtly in depth to intensify an emotional story point. Jhun describes how this worked for a pivotal scene with Shrek and Rumpelstiltskin talking in Rumpelstiltskin’s carriage.
“As the scene became really intense,” Jhun says, “we brought the characters close to the audience and pushed the background farther back even though the [carriage and characters] did not move. It created a slight uncomfortable feeling in the audience. Without any dialog, you can tell this is an intense scene, that something is not quite right. You can feel it.”
Techniques such as that, which the layout artists used during shots and during cuts, helped create a depth rhythm to support the story. “We put a lot of energy into designing shots,” Jhun says. “This is the last movie, the final chapter, and it’s in 3D, so we put a lot of effort into making it more dramatic.” In addition to the 3D techniques, the layout artists used camera drift and longer shots to enhance character emotion and give the film a more sophisticated look. And handheld virtual cameras gave a traveling sequence a documentary realism.
During a sad, serious sequence with Shrek and Fiona, for example, the camera drifts in and out as the characters connect and disconnect, and for this sequence, the stereo is neutral. “Some directors with an animation background are genius directors, but they fall in love with a storyboard or image in their mind before it comes to layout,” Jhun says. “Mike [Mitchell], who was a live-action director, gave us the opportunity to explore scenes with a camera.”
Animators started performing the characters blocked into the scenes once the layout was about 70 percent close to final. When animation was final, the layout artists did another stereo 3D pass and brought the scenes 95 percent close to final. “We give the animators the camera, but we know some shots should be driven by animation,” Jhun says, “so we redo the camera based on the acting.”
The layout artists tweaked the last five percent once lighting had finished. “Sometimes the scenes look really different with light and textures, and the stereo 3D becomes a little overwhelming,” Jhun says. “And other times, we ramp it up a tiny bit more to make the shots more sophisticated.”
Jason Reisig, who was an animator on the first Shrek, led a team of approximately 35 animators who he organized into four teams, each with a supervisor, and then organized the work by sequences. “The animators on Dragon used a traditional animation workflow, which made sense because they had a significant number of hero characters,” Reisig says. “We had fewer main characters and many sub-characters, so the supervisors cast teams of animators per sequence, and in those shots, the animators worked on all the characters. It kept us light and flexible.”
For reference, the animators have Webcams at their desks and acting rooms where they can record themselves. In addition, for a battle between the ogres and witches, they mocapped three people doing fighting moves. “The cycle animators played with that motion-captured data and used it as reference,” Reisig says.
In the early days of PDI/DreamWorks, and for the first Shrek film, the rigs for the characters, which were mostly bipeds—if not human, then human-like—included restraints you would expect in a human character. Animators could rotate a character’s shoulders, hips, and head in only very specific, anatomically correct ways. For the cartoony characters in Madagascar, the studio created a more flexible rig, which the animators have used since, even for non-cartoony characters—except for those in the Shrek films. Reisig asked for a change. “I said that we had to get rid of the old, stilted Shrek rig,” Reisig says. “We had to have a more flexible rig. The old one was too puppet-like, and it was causing problems with the animators. So on the legacy characters, we tried to keep the basis of the classic rig and retrofit a new system. For the new characters, we used all the newest methods we had.”
The task of retrofitting the newer types of controls onto the classic rigs and fitting the new characters with new rigs fell to a group of character technical directors led by J.J. Jay and Andy Kao. “We wanted to allow animators to get a broader range of acting, so we started with the existing rigs and folded in the newer controls,” Jay says. “The technical challenge was to allow the animators to do the things they are used to doing now without changing the look of the characters as they deform.”
Animators working with the new characters, and new versions of the old characters, though, used RIG, the new system. “One of the advantages of having a homegrown tool is that we can take a [rigging] concept and do what we want with it,” Jay says. “For example, we use our elastic cage deformation quite a bit as a lower-level part of our deformation.” This was key in animating Puss In Boots, who becomes a fat cat in Shrek’s alternate reality. A fat cat that sometimes walks upright on two legs, and sometimes gets down on all fours. When Puss changed from biped to quadruped, his hips and shoulders changed, and his belly had to move appropriately. The portly Puss also had to deform properly—and automatically—when the animators positioned the character in what Jay calls “interesting poses.” (DreamWorks is submitting a SIGGRAPH sketch on the techniques the TDs developed to move Puss’s plump body.)
“We played around with keeping the elastic cage the same distance from the joints that drive it, which gave us fake volume preservation,” Jay says. “We had to do some layering and localized blending, but [the rig] provided nice shapes right out of the box, and it allowed the animators to see the deformed body. There was no simulation; it was all animator-controlled. They didn’t have to rely on a downstream department.”
TDs retrofitted new controls onto the classic rig used for many of the legacy characters in Shrek, like Shrek and Donkey (top), but to move the now-pudgy Puss In Boots (bottom), they applied a newer and more flexible system aptly named RIG.
The flexible RIG extended into character design, as well; the TDs used the system to reshape a generic character into a variety of individual characters. “Sometimes the art department drew variations and we tried to hit them,” Jay says. “Sometimes we needed help from the modeling department. But the TD department did most of the variations.”
To create more than 16 types of ogres, the riggers started with a default body and individual rigs for each of the four ogre families. “Once we get the rig working with the default model, we can use the animation controls to create variations,” Jay says. “We can go a certain percentage in any direction with the rig and it behaves well. The deformation allows us to create pleasing shapes by varying the body and the face. Then we lock in the controls.”
In addition to providing sculpting controls for character variations and preserving Puss’s pudgy volume, the rigs also moved most of the characters’ hair and fur automatically. Consider a character that shakes its head, for example. “The animator would focus on the head movement and then initiate a simulation pass,” Jay says. “The system would execute their animation and modify the values for the guide hairs. When the animator looks at the shot after simulation, the hair is moving on its own.” If the animators didn’t like what they saw, they could change simulation controls or hand animate the motion by moving the guide hairs.
In Shrek’s alternate reality, though, Fiona’s long hair required a separate simulation by the character effects team. “It’s wild, and it falls over her shoulders in front and behind,” Jay says. “Putting that into the rig would have impacted its performance.”
When we first see Fiona, she stands atop a hill. She pulls off her helmet and her luxurious, long, red hair blows in the wind. “Her wavy, flowing red hair is an integral part of her character,” says visual effects supervisor Doug Cooper. “Our character effects supervisor, Oliver Finkelde, started with the long hair system for Shrek 3, looked at the tools in Maya and Syflex, and put several pieces together to develop a new hair system for the film.”
In addition to updating the rigs and developing a new hair system for Fiona’s locks, Cooper points to new setups for multiple-layered clothing, a magical “poof,” and a world-changing event as interesting technical challenges on this film.
For the clothing, the character effects team developed a system that could simulate multiple layers of clothing at the same time. “Before, we had done multiple passes with one layer becoming rigid for the next layer’s simulation,” Cooper says, “but the look wasn’t believable, especially when you had a thin under-layer pushing around leather on top. Sometimes people in production take things for granted in legacy films, but Shrek has been in development 14-plus years. Nothing just loaded and ran.”
Layout artists kept the stereo neutral and used traditional techniques, like camera drift, to heighten the emotion in some dramatic scenes, such as those between Fiona and Shrek (top). For the intense scene between Shrek and Rumpelstiltskin (bottom), however, they applied stereo depth purposefully to drive a feeling of discomfort.
Alex Ongaro, head of effects, led the teams that created the magical poof and spun Shrek into and back out of alternate reality, with effects artist Andrew Kim contributing to both. The poof is a filigree pattern of gold dust that occurs when Shrek signs the magic contract and at other points in the film. The technique involved directing particles to follow modeled shapes yet still react to wind and other dynamics in a scene. “Imagine bi-dimensional swirling particles,” Ongaro says. “We animated the particles procedurally, saved them on disk, and then instanced those geometries into a Maya scene that was dynamic, so the wind and turbulences affected them.” (DreamWorks is submitting a SIGGRAPH sketch on this procedure, too.)
Once Shrek signs the contract, the world he knows rips apart into a storm of papers that fly around and reassemble into an alternate version of the world that Shrek thinks, at first, is the same world. Ongaro again worked with Andrew Kim on this world-changing event.
“We started developing the concept while the movie was still in storyboards,” Ongaro says. “We decided that since everything centered on the contract, why not imagine that the world is made of paper that tears apart?”
To create the effect, the artists used a combination of tools, including Side Effects Software’s Houdini. They started by building a simplified version of the set using simple planes, which sounds easy enough. “The problem was that this is a stereo movie,” Ongaro says. “We needed to go from a 3D movie to effects in paper.” The answer was to render the final lighting version of the scene from both eyes and then project the images on to the set made of simple planes.
“Basically using projection mapping from the camera and the two different eyes gave us the 3D effect once it was on the planes,” Ongaro says. “We took this environment and tore it apart procedurally in Houdini. From Houdini, we knew where the edges were, so we could have them affected by fields. The paper needed to deform, but instead of doing that in Houdini, we did it at render time with a displacement map, a world-space noise map.”
In addition, they sent a spherical tornado of gold light into the scene as the world tears apart. “It was very challenging,” Ongaro says. “The lighting department had to update the papers like they were tearing apart, with light coming from the outside.”
The tornado is made of millions of particles, which needed to look as if they were backlit, as if they had subsurface scattering. Custom tools handled global illumination and ambient occlusion within the tornado, but the self-shadowing didn’t look right. “We decided to compute normals from the particles to do a quick and dirty ambient occlusion pass,” Ongaro says. “We’d take a group of particles, compute the difference between the vectors, and get a gradient. We’d point the normal in a less-dense area.”
In addition to these effects, the team grew trees with a previously developed system, poured martinis using Maya, kicked dust with Maya particles, filled the air with smoke using a volume renderer, and helped the characters create mud angels using particles and displacement maps. Perhaps the most beautiful effects, though, are the god rays filled with glittering dust.
“The beams of light come into the audience, and you can almost taste the dust,” Mitchell says. “You want to run your fingers through it. It’s bizarre.”
For this effect, the artists developed a particle shader within the studio’s proprietary rendering system. “We couldn’t create the god rays in compositing because this is a stereo movie,” Ongaro says. “So we used particles as the source of the rays, and at render time, filled cones with particles that fade off. It turned out to be beautiful.”
Even though this is the last Shrek film, it is not the last reunion for at least some of the familiar characters. Already under way is a film titled Puss In Boots, which is scheduled for 2011. And with DreamWorks promising three films a year in the future, many of the crew on this film will reunite on another film. In the 10 years since DreamWorks Animation created the first Shrek, which won the first Oscar for Best Animated Feature, computer graphics technology and the artists using it have advanced at lightning speed. But, they aren’t out of school yet.
“We have a lot of experience and great artists who are masters of their craft, but they just keep getting better,” Cooper says. “Everyone’s skill set and ability and understanding of what they are building and making allows us to keep making richer pictures. We’re always coming up with new techniques. We take so much for granted, but in fact, no one is a total master of this medium because the medium hasn’t been around long enough to be mastered.”