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18 ■ CGW M ay / Ju n e 2 014 VIRTUAL HUMANS calls a "crazy, broad range of facial expres- sions," none of which would appear in the movie but that the team could use as charac- ter studies. "Understanding the human face, the essence of a character, was an interesting learning process," Port says. "It's one thing to do a caricature for a static image, but in the animated world, there are expressions. We probably did a few thousand iterations." Using a consistent strategy as much as pos- sible, the team gave all the pixies larger heads, pointy ears, larger eyes, and slightly smaller noses, but varied the shapes, proportions, and relative distances between the eyes, nose, and mouth. Then, they transferred the face shapes and rigs created for the CG versions of the actors to the pixie models using tool sets devised for the task. "We did most of our work on the [CG] actor's face," Hendler says, "and then transferred the face shapes to the new [pixie] facial anatomy. The pixie design changed through production, so having tool sets that automat- ed this process was great." Each pixie's face might have as many as 3,000 shapes. "We've done a lot of work on our facial rigs," Hendler says. "In the past, we might have a linear transition between one expres- sion, one face shape, and another. Now, that same in-between might have 10 face shapes. We have a huge number of shapes around the eyelids to have the skin unfold and lift up." Each CG model of an actor and the CG model of the actor's pixie had the same rig design – the same settings. "We made sure our pixie's face matched the nuances on the actor," Hen- dler says. "If an animator gave the actor a 50 percent smile, the pixie would have a 50 percent smile. The animators could switch back and forth. That was crucial." Once the animators were satisfied with the shapes and rigs on the pixie model, they could work with the data captured on the motion-capture stage. "Transferring the data from the camera to the rig is an area we improved upon," Port says. "We're taking the data and ap- plying it so fast now that animators can do it themselves. The tracked data comes in. Someone hits a button. The tool set processes the data and puts it onto the rig quickly. It's a darn good starting point. The challenging areas are around the eyes and mouth." The Eyes Have It The tool set moves the motion-capture data onto the pixie body and, separately, onto the face. "We had a moving point cloud with 200 points representing the actor's face," Hendler says. "Our solver takes those 200 points and transfers them to the [CG] face. Then, it's up to the animators to enhance, refine, and work on regions that weren't captured fully." Once the data is on the pixie rig, animators can see the pixie face moving with the actor's expressions as the actor speaks Blood Flow Beneath the Surface As digital doubles edge closer and closer to photo- realism, visual effects artists continue to find subtle additions that provide an extra bit of physical reality. For this film, the artists at Digital Domain sent blood flowing beneath the skin of the pixies' digital faces. To do that, they first had the actors playing the pix - ies perform a range of expressions under a specific cross-polarized lighting setup at ICT to see how muscle motions affected blood flow. "We had them hold an expression and then relax," says Darren Hendler, digital effects supervisor at Digital Domain. "Then we timed the rate at which the changes in blood flow would occur under the skin, the number of frames. This is something we'd never done before. We could see how muscle motions affected the amount of blood under the skin. If the actor scrunched her face, her face got redder. If she compressed her lips, the blood drained out." The artists soon learned the effect has to be subtle. "If you put it in full tilt, you get a red face very quickly," says Kelly Port, visual effects supervisor at Digital Domain. "So we had to dial it in. There is a transition, a time delay, when the blood is pushed out or flowing back into the skin. To my knowledge this hasn't been represented be - fore. Adding it is unique. As subtle as it is, it takes us one more step toward being realistic." – Barbara Robertson Maleficent in Action ■ MOTION-CAPTURE DATA underlies the pixies' performance and expressions.