Issue: Volume: 23 Issue: 12 (December 2000)

Digital Dogs

by Barbara Robertson

How do you teach an 8-week old puppy to hang onto the back of a moving train? You don't-even if the script calls for it, as does the script for Walt Disney Pictures' movie 102 Dalmatians. This sequel to the 1996 film 101 Dalmatians puts Glenn Close in the spotlight once again as evil fashion designer Cruella de Vil, who repeats her attempt to turn a cute pack of puppies into the ultimate fur coat. Directed by Kevin Lima, who previously directed Disney's animated film Tarzan, the live-action comedy has Cruella chasing puppies through the streets of London and Paris.

In the 1996 movie, the dog stars were the two adult dalmatians, with 99 puppies in minor roles. In this movie, all 102 dalmatians are puppies and the dog star is an all-white, 8- to 10-week-old dalmatian pup named, appropriately, Oddball. Visual effects, which for the most part involved spot removal and digital dogs, were created by Disney's The Secret Lab.

The Secret Lab (TSL) was formed when Disney merged its animation and effects studio Dream Quest Images with its in-house 3D animation group. 102 Dalmatians, the first big project undertaken by the merged groups, uses techniques developed separately at Disney for Dinosaur and at Dream Quest Images for a variety of previous movies. Together, the teams also created new techniques to handle the visual effects for this movie-spot removal for Oddball, a digital stunt Oddball, and digital puppy extras. In addition, the crew helped a Macaw talk.
For the scene below, the crew painted out supporting platforms. For the scene at right, they multiplied puppies with split-screen techniques. The white puppy's spots were removed with 2D graphics.

One of the challenges for TSL was that the puppy playing Oddball kept changing. The filming was spread across a six-month period, and puppies grow quickly, so every two weeks, a new litter of dalmatian puppies would show up. The dog trainers would pick the smartest puppy or puppies out of the new litter to be the new Oddball, regardless of gender, spot patterns, or ear color. When Oddball and her littermates turned 10 weeks old, they all became extras for two weeks-Oddball was supposed to be smaller than her brothers and sisters, so the age difference heightened the illusion. With spots back on, the puppy playing Oddball would blend into the rest of the pack.

To create the all-white Oddball, the effects crew implemented several techniques. Using Discreet's (Montreal) Combustion program, they could track the spots in each frame as the pup moved through a scene and automatically replace the black color with white in each frame. When there was too much motion, the cloned spots were touched up by painters who used Avid's (Tewksbury, MA) Matador software. For pups with black ears, the crew would paint a white ear, then, using Avid's Elastic Reality, would replace the real ear with the puppy's new ear and add animated shadows. When none of these techniques worked, the team resorted to 3D solutions for digital spot removal.

"We had one shot with a puppy playing Oddball that had big black blotches all through its chest and face," says Dan DeLeeuw, co-visual effects supervisor. It became so difficult to remove the black without losing details and expression on the puppy's face, particularly around its eyes, that the effects team decided to try substituting a digital puppy. Until then, the team and the director had considered using a digital Oddball only for stunt work.
Is she real or is she digital? This puppy, one of several who played the role of Oddball, is a real dalmatian. Her spots were digitally removed at The Secret Lab.

"We could see that we were getting a bit of magic happening with our CG puppy. So, we took a chance," says DeLeeuw. "On our own, we put the CG puppy into the scene. We matched the action, lit the scene, rendered it and then had the director come in to look at spot removal shots. He watched the shots and didn't say anything, so we showed them to him again, and then again and asked him if he saw anything funny."

"I knew something was up because they kept asking me if everything was OK," remembers Lima. "Usually, they never ask if anything is wrong because they want me to OK scenes."

"He spotted the digital puppy when it blinked," says De Leeuw, who explains that since the real puppies never blinked at the right time, Lima knew the blinking puppy couldn't be real.

"In that moment, I knew we didn't have to be afraid to use digital puppies," says Lima.

Fortunately, TSL was prepared to have the digital puppy substitute for the real puppy in closer shots. "We always wanted to do more than stunts, and in the end [that preparation] paid off," says DeLeeuw. To create the digital dalmatian, the team started by sculpting maquettes using reference photos and puppies they brought into the studio in California. The digital model was then built in Alias|Wavefront's (Toronto) Maya. Later, they would discover that the English dalmatian puppies used for the filming in London and Paris were smaller and lighter than their American cousins and they had to resculpt the puppy.

Once the model was built, a team led by CG supervising animator Rob Dressel created a standard IK "rig" for a digital quadruped in Maya. Then, to make the motion more realistic and the animation easier for the animators, the team created Mel scripts that would generate the IK rig on the fly. A quadruped needs two centers of gravity, so the team wanted to give the animators the freedom to pull the digital puppy's bones forward with the shoulders or back with the hip, something that is not possible with a typical model's hierarchy. Thus, "Instead of loading the entire file with the model of the dog, we ran it like software," says DeLeeuw. "It created the dog on the fly." If an animator picks a hip object, the hip leads and the shoulder follows and the skeleton is drawn back to front. If the animator picks the shoulder object, the hip follows, and the direction in which the skeleton is drawn is re versed. "Fortunately, we had X-rays of puppies to work from," says DeLeeuw. "The shoulder slides as it should. It's not just a ball and socket."

For facial animation, the team used a proprietary program called Framer, also written in Maya's Mel scripting language, that uses the software's sculpt objects and deformers to give animators an alternative to shape blending. "I try to avoid blend shapes because I think you can often see them," says DeLeeuw. "I like to use bladders under the skin that inflate and deflate and to have wires that pull the skin. The face needs so much detail. We have as much complexity in the eye, eyelid, and lashes alone as in the rest of the puppy."

Once the model was animated, it was sent to a "skin and muscle" department. Usually, a CG model is made only of skin and bones and the bones determine skin movement, but with this type of model, it is difficult to maintain mass in areas such as shoulders. For the puppy, TSL decided to use a system developed at Disney that puts muscles between the bones and skin. "The muscles are simple tubes that flex and expand based on joint rotations as the skeleton moves," explains Dressel. The skin is attached to the muscles and follows along as the bones move the muscles. To add realism, the system offers an interactive process that relaxes the skin so that it doesn't look too tight as it's pulled by the muscles, adding inertia to the movement. For the hair, the team used the same fur program used at Disney to create hair for the lemurs in Dinosaur.
Above, from left to right: Working in Alias|Wavefront's Maya, TSL's visual effects crew created the model, then "chained" it; that is, created bones for the IK rig. The third picture shows the muscle system to which the skin was attached (fourth p

"Certain things tell you it's a puppy. Puppies never stop moving, so that has to be right, its physiology has to be right, and for the hair, lighting is the key," Dressel says.

"I think the hardest shot was the initial shot," says DeLeeuw. This takes place in the parole office and involves a sequence in which Oddball tumbles out a window. "We were cutting back and forth with the live action dog-Shake to fake," says DeLeeuw. Shake, from Nothing Real (Venice, CA), was used to composite the film. The digital stunt puppy also barely makes it onto the Orient Express and, once in Paris, finds itself covered with batter in a patisserie. The CG puppy acts in daylight and at night, in scenes with people and with other puppies-some of which might also be digital.

TSL put extra spotted digital puppies into scenes that called for many puppies to help fill in the "holes" and to interact with the actors. A digital puppy runs between Cruella's legs in one scene, for example. "You can control one puppy on the set," says DeLeeuw. "But when you get more, anarchy rules."

All told, TSL worked on 345 shots for the film including platform removal shots, of which 30 had digital puppies. Although the fewest in terms of number of shots, the digital puppies may have the most impact on filmmaking in the future because they looked so real.

"When I saw how well the digital puppies lived in the real world, it made me realize that we could do anything," says Lima. "That's incredibly freeing and also incredibly frightening. Now I have to conceive what anything could be."

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