Issue: Volume: 25 Issue: 5 (May 2002)

Free Spirits

By Barbara Robertson

On May 24, DreamWorks Pictures, the studio that brought the world Chicken Run and Shrek, will release a film that takes animation on a new high-stakes ride. More than four years in the making by 300 artists, animators, and technicians, that film, Spirit: Stallion of the Cimarron, tells the story of a wild mustang in the Old West, the leader of a herd of horses who fights for freedom-his freedom and that of his herd.

Here's the risk: Unlike last year's box office busting animated features, Spirit is not a comedy and it isn't a 3D animation. Filmed in wide-screen Cinemascope, Spirit tells a dramatic story using traditional 2D animation, but with a 3D twist. Dream Works calls the new look a "bold move to reinvigorate a movie-making tradition" and a "ground-breaking reinvention of traditional animation." What's more unusual is that in this film, there's very little dialog. The art and animation tell the story.
For close-up performances, animators creating hand-drawn characters often referred to animated cycles of 3D clones for volume, scale, and perspective changes.
All images courtesy DreamWorks Pictures.

"This isn't 'The Stallion King,'" laughs Kelly Asbury, co-director (with Lorna Cook), referring to Disney's popular animated film, The Lion King. "There are no talking, singing horses and animals. We have a few human characters who deliver key moments of dialog, and Matt Damon narrates as Spirit recollecting his story, but there's no lip movement [for horses], and the narration is sparse."
These horses are 3D elements, as is the water. Effects artists used the studio's "spryticles" system to make the splashes near the horses look hand-drawn.

To create most animated films, animators construct performances for characters that complement prerecorded dialog, often using videos of actors speaking lines as reference-Eddie Murphy as Shrek's donkey, for example. Even Fantasia was animated to a musical sound track. By contrast, all the animation for Spirit was finished be fore final narration was recorded and be fore songs were written. "For all intents and purposes, it was made like a silent film," says Asbury. "I like to think that the narration, dialog, and song serve the same purpose as placards did in silent films. At its core, Spirit's story is told through as many visual means as possible."

To create backgrounds and characters for Spirit, the studio used a combination of 3D computer graphics and hand-drawn 2D images. It's a combination Asbury believes makes this film strikingly different from other animated features.

Spirit's world is largely created with 3D graphics to give the directors freedom to move the camera. "We wanted to use the camera as a storytelling device," Asbury explains. And indeed the camera sweeps through grand landscapes, moves 360 degrees around characters, and follows Spirit on a joyous run. But, to give 3D backgrounds a painterly look, the models were textured with paintings created with traditional media. "We wanted to take the audience into backgrounds that captured the look of Remington and Charles Russell paintings," says Asbury.

The characters in Spirit also reflect the studio's skill in both types of animation. As in previous films from DreamWorks, crowds (animals, cavalry, Indians) were often 3D. New with this film are main characters that switch from 2D to 3D. The 2D horses provided the close-up performances; the 3D characters were used primarily as digital stunt doubles in medium to long shots and for complicated 3D camera moves. So, given the success of 3D characters in other films, why did these filmmakers choose to use hand-drawn characters?
To create fire and smoke, the digital effects team used particle dynamics with the motion of fire (top), mapped sprites-hand-drawn animations of flickering flames-onto the particles (middle), and caused smoke particles to be emitted as the particles on th

"There was a time early on when we considered having the horses talk," says Asbury. "But we found that when horses start talking, no matter how seriously, we're into Mr. Ed and Francis the talking mule territory. The only time horses talk in movies is for comic effect. And this is not a comedy." Yet, the horses needed to have facial expressions and that, the directors decided, ruled out 3D. "We didn't want a cartoony horse in the way that the donkey in Shrek is cartoony," Asbury says, "and we felt that a realistic 3D horse with facial expressions would have looked strange because horses don't naturally have the kind of facial expressions we wanted, but 2D offers a huge, beautiful range of emotions. We felt the hand-drawn designs were a more dignified way of telling our story."

Thus, when Spirit, his love interest Rain, and other horses showed emotion, their performances were created with hand-drawn animation. And this animation was a challenge: Because the film is not a 'toon, the horses had to move like real animals; there would be no squash and stretch. For reference, animators spent hours watching and sketching horses at a nearby equestrian center, and in particular, a Kiger mustang, the breed of horse most nearly like mustangs of old, purchased by the studio specifically for this purpose.

To help keep performances consistent between hand-drawn horses and their "digital doubles," many animators worked with both techniques. "We trained a number of our traditional animators to animate in 3D so that we could get the same performance in both cases," says Doug Cooper, digital supervisor. Then, to blur the visual distinction between the 3D and 2D horses, the studio rendered the 3D horses without textures using a 'toon shader and developed a new technology called SuperTones that gave 2D horses a three-dimensional quality. The result is a film with the freedom and dimension found in 3D animations and the painterly, hand-drawn quality of a 2D film--but with a look that's unique.

For inking and painting 2D characters and for compositing, DreamWorks used a modified version of Cambridge Systems' Animo. Characters were drawn in pencil and scanned into Animo; similarly, backgrounds and background textures for 3D elements were painted, scanned into Adobe Systems' Photoshop, digitally manipulated, and then imported into Animo. For creating 3D backgrounds, characters, and many effects, DreamWorks used Alias| Wavefront's Maya and rendered the 3D geometry with Pixar's PR RenderMan; some particle effects were rendered in Maya and composited with Apple/Nothing Real's Shake before being fed into Animo. In addition, the Spirit team's proprietary software helped blend 2D and 3D worlds and create effects. During this film, the studio began its transition from SGI's proprietary Irix and hardware to Linux running on PC hardware from HP.

One scene that exemplifies the combination of technologies in Spirit is the opening three minutes, the so-called Homeland Pan, which introduces the audience to the vast landscapes of a mythic Old West. Think Utah, Yosemite, Grand Canyon, Yellowstone. An animatic for the sequence took nine months to develop; the scene's 4183 frames took more than two years to complete.
Even when the horses Spirit (at left) and Rain were hand-drawn, as in the scene at right, the animators would often use animated cycles of 3D versions of the characters printed onto animation paper as reference for perspective, volume, and scale.

Some 1800 separate pieces of painted artwork were projected and blended onto 3D geometry to create the environment, with another 700 paintings used to create trees, skies, and mountains. Effects created in Maya helped artists add geysers, rushing water, blowing grass, fire, and moving clouds. Buffalo, running horses, and an eagle were also created with 3D graphics; the deer, bears, and salmon were hand drawn. In a separate dramatic sequence, hand-drawn horses are swept into a river and down rapids. The water is 3D mixed with some hand-drawn splashes.

To create environments, a layout artist started with simple 3D geometry for the backgrounds in Maya and determined camera views using animatics as reference. Those views were printed and given to artists who added details to the geometry by drawing on the printouts. Their drawings were scanned and projected back onto the geometry in Maya and when approved, sent to the background department, where final paintings were created. Those paintings were eventually scanned and used as textures for 3D models.

Although some effects were added to these painted 3D environments traditionally, many were created with 3D graphics. All told, a team of 16 people headed by Wendy Rogers, digital effects supervisor, produced 700 effects shots for Spirit. "The most challenging effects were the organics," she says. "They had to fit with background paintings, which were beautiful, and 2D characters, which don't have much detail."

Many organic effects were created with the help of sprites. For example, to create fire, effects artists would map pieces of hand-drawn, animated flames, what Rogers describes as a little cycling piece of flickering flame, onto 2D cards. The cards were then animated with particle dynamics to simulate the motion of fire. Similarly, animated splash cycles were mapped onto cards to create water sprites, which were then animated with particles set in motion to look like flowing water-a technique that DreamWorks has named "spryticles."
Using 'toon-shaded 3D models, the effects department created a train-crash sequence, with particles and sprites (spryticles) forming dust. By providing a 3D chain for the hand-drawn Spirit, the studio helped animators save time.

For the water sequences, the crew typically used 3D water and 3D splashes, except for splashes around 2D horses. "If you create a 3D splash, it's foamy and volumetric," Rogers says. "It doesn't look like a hand-drawn splash. There are more droplets." To blend the two types of splashes, the crew used spryticles to fit the hand-drawn splashes near horses within 3D splashes. The water surface was created with RenderMan shaders. "Because the texture is based on the same motion as the particles, it feels cohesive," Rogers says.

The team created moving grass, on the other hand, with Maya fur. The effects artists built libraries of sod-little bits of turf, each with its own characteristics-that they placed in scenes as needed. "I feel that even though we had a large volume of effects in this movie, we worked hard to allow the effects to be controlled artistically, not technically," Rogers says. "There were no push-button solutions. The artists could be artists."

For placing 2D characters into 3D environments, DreamWorks used proprietary software originally designed by Dave Morehead and co-developed by SGI and first used for Prince of Egypt. For Spirit, DreamWorks turned that software, called Exposure, into a Maya plug-in it calls ToonStage. "We build the environments in 3D," Cooper says, "and then ToonStage allows us to place a piece of paper in that 3D environment. It helps us take elements from the 3D world to the physical drawing desk and from there back into the 3D world again."

Often, though, the characters inside 3D environments were 3D. "We used digital characters for herds of horses, cavalry men, and Indians," says Cooper. "And we also found there's a cost savings to use digital animation for a lot of shots of the main characters. So we built and rigged full CG versions of Spirit and Rain for medium and long shots and for shots with complicated 3D camera moves." Thus, in several shots, Spirit changes from 3D to 2D and perhaps to 3D again.

The "take-over" from one type of animation to the other was smoothed by having traditional animators work with both types of technology and by the astute use of technology to blend looks. First, the entire shot was animated in 3D, with parts that would later be hand drawn animated more simply. This 3D animation was rendered with a 'toon shader and printed. Traditional animators used these rendered images as reference for the transition from 3D to 2D, precisely matching the animation for a few frames. Once their drawings were completed and scanned, the crew adjusted the parameters in the 'toon shader to match the line thickness on the 3D horse to the scanned drawings. Finally, to match the lighting for both types of horses, the crew used a new 2D imaging technique they created and named "SuperTones." "Traditionally, artists draw shapes on characters to create tones and those tones are blurred consistently across the characters," says Cooper. "But this doesn't really describe the volume of the character. We needed a more effective method for creating realistic lighting."

With SuperTones, effects artists controlled how soft or hard the horse looked in various areas of its body and the software created transitions between areas. "What's key about this is that areas where the bones are close to the skin can look sharper than, for example, a horse's lower belly, which is smooth and round," says Cooper. "With traditional tone mattes, it would all look the same." The result was a realistic level of shading that looked 3D, but without textures. "We created some tests in which we added bounce lights and highlights, but decided not to use them because it began to look too much like a 3D movie," he says. "What we wanted was a way to raise the bar on visual complexity without changing the medium."

In creating this film, the crew for Spirit has used a hybrid of technologies that may point the way toward a future in which, Cooper believes, people will no longer draw a distinction between 3D animation and traditional animation. "I think we're going to see more painterly and stylistic 3D films," he says. "As the technology is blending, so too are the creative styles."

Barbara Robertson is Senior Editor, West Coast for Computer Graphics World.