CGSociety

George Clooney tries Goat Tipping at CIS Hollywood.

CGSociety :: Production Focus
19 November 2009, by Renee Dunlop

Sometimes the smallest animations can have the biggest impact. In George Clooney’s latest film, 'The Men Who Stare at Goats', he plays a character who believes he has the psychic power to control his surroundings. While the FX were nominal, they were pivotal in achieving this storyline.

GOAT GATHERING
The biggest challenge was creating a photorealistic goat that would cut seamlessly with a live action goat in surrounding shots. At the end of the sequence the goat collapses after Clooney’s character Lyn Cassady, seemingly stops the goat's heart using the power of his stare. It was important the CG goat was identical to the live action one, that the comedic timing was precise and believable, and that the goat fell in a way to evoke a reaction of humor rather than concern for the goat's safety. That one 140 frame shot had a lot of responsibility.

Visual Effects Supervisor Thomas J. Smith gathered reference of the live action goat while on set in Puerto Rico, collecting image data from the front, side, back, three-quarter view, and details such as hooves, ears, and facial features for close-up texture reference.

The digital goat was modeled and rigged in Maya. Explained Henke, “we posed the rig of the goat in the plate and further tweaked the model to match the live action goat. In addition we scanned the surrounding shots and lined up 3D cameras to gauge the model’s proportions from different views - we didn’t want to end up faking a part of the anatomy that matched the fore-shortening of the goat standing but became unappealing when the goat fell down.”

Goat Lighting / Look Development / Fur Design was handled by Charlie Winter. The goat fur was primarily handled with Joe Alter's Shave and a Haircut, a popular hair and fur plug-in for Maya that use curves as guides for the direction the fur is oriented and integrates well with CIS’s RenderMan pipeline. “We used Maya’s Hair tools to create guide curves for Shave, a technique that ended up being a great way to style the fur in broad strokes,” said Henke. “Then we did some finer detail work using Shave's grooming tools. The color of the fur was derived from color maps created using the reference photos of the live-action goat, with a graded translucency along the length of each follicle. We used Maya's lighting tools to render in RenderMan, as well as conventional shaders for the fur’s surface qualities.”

It’s important when rendering fur that it accurately self-shadows, casting shadows from the fur onto itself and the surface it’s covering. Typically CIS would approach fur self-shadowing with shadow maps from spot or direction lights since the maps can be softened and are much less computationally expensive than rays bouncing between the follicles. However in this film, the goat’s environment had a lot of bounce light and lent itself to the indirect lighting best achieved with global illumination. “In order to achieve this amount of indirect lighting and shadow quality we opted to go with ray tracing and global illumination in RenderMan. The ray traced self-shadowing gave us finer detail without being limited by the resolution of a shadow map.” The cost was in the rendering time, roughly three hours per frame.

Stop and Drop
Animation, handled by Brett Magnuson, was a huge concern, probably the most subjective aspect of the shot. The goat’s collapse was the climax of a comedic sequence and the timing had to work perfectly without pulling the audience out of the scene.

Breaking down the scene, the goat goes through three behaviors: from standing idly to being transfixed by Lyn’s stare to collapsing lifeless onto the floor. At the transfixed stage, they strove for a freeze that still had a feeling of life. “The timing in the follow-through in the ears after this change became something we wanted more and more control over. Initially we were treating the ears as a cloth simulation, like thick canvas, but we opted for keyframing during the animation. A beat ensues, enough time for the audience to understand that there's a connection going on between the two characters.

Next change is the goat’s collapse. The idea was to give the goat a feeling of instantly losing control, as if it's heart had been stopped. We approached this by leading the fall with the goat’s chest. We had to be careful about how hard the goat hit the ground in the animation; too hard and the audience would shift its sympathy to the goat and away from George's character.” CIS had specific model sculpts to address how the goat's belly and flesh were shaped while it was lying on the ground. They utilized blend shapes that enhanced the result of the deformations from the rigging believing it would be impractical, and probably not as appealing, to try to achieve those results from muscle or fat sims.

Much time was spent in the screening room comparing the live action plate of the goat with the CG goat in order to match the lighting, textures, and proportions. There's a slight change in focus along the length of the goat, and this depth of field was handled in compositing with a z-depth pass. “In these sessions we'd determine where the best part of the process was to tackle each issue. In the case of modeling, we’d determine if we’d change the shape via posing the model or creating a custom sculpt; In the case of lighting, we’d determine whether to address the tweak in either the texture or compositing.”

FLYING THINGS
Another CG creature was a butterfly that lands on Clooney's hand; he blows the butterfly off and it flies away, landing on an apple in the branches above as the camera follows its flight path. “We rendered the wings using sub-surface scattering to capture translucency of the wings. The sub-surface scattering gave us a more complex result than an evenly distributed opacity value. The iridescent quality of the wings were created by attaching a volume light to the butterfly - we'd get glints as the wings moved through the volume and hit angles that gave us a direct reflection to the camera.”

Other CG elements in the show are Huey and Kiowa helicopters, signs, background and set extensions. There are sequences shot in Glamis National Park and White Sands, New Mexico for scenes set in the deserts of Iraq. A few of these desert shots required inserting matte paintings to clean up tire tracks, road signs, or any other indication the desert wasn’t in a remote part of Iraq.

One shot followed the camera down some steps through locked glass doors, through a dark room, and then through another set of locked doors into a room that acts as a pen for goats seemingly kept for telekinetic target practice. “We had two shots, one with the camera moving down the stairway and through an empty doorway, and the other a tracking shot into a room with goats and hay on the floor.” Smith and Director Grant Heslov wanted the shots joined seamlessly for a continuous shot under a voice-over. “To do this,” said Henke “we built a CG room that the camera passes through, and this acted as a place to transition the camera moves while being constrained to a live action camera. The two shots had different focal lengths, and we thought we would have to incorporate a zoom during this transition between the two cameras… which in this context would just look weird. Our solution was to get a good-enough camera track of the B shot using the focal length of the A shot. This worked well enough to move from our CG elements into the live action plate without having to incorporate a zoom.”

Sometimes, it’s the little things that count.

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