Although the superhero in My Super Ex-Girlfriend doesn’t show up in blue tights and a red cape, G-Girl (Uma Thurman) still throws her weight around thanks to a supporting cast of VFX artists. Digital Domain muscled through 220 effects shots, tossing a digital shark through a bedroom window, electrifying hunks of rock to create supercharged meteors, and distorting a few backgrounds when G-Girl felt a need for speed.

“We were on a very short schedule,” says Erik Nash, visual effects supervisor at Digital Domain. “Ten months from prep to final delivery. But this is not like Spider-Man, where you’re blown away by the visual effects. At the end of the day, this is a romantic comedy that happens to have a superhero as a lead character. Our job was to help the comedy along, reinforce the laughs, and maybe once in a while, like with the shark, provide the laugh.”

G-Girl tosses the shark when she discovers her boyfriend (Luke Wilson) sleeping with a co-worker. The shark lands on Wilson's bed, flops around on the floor, and then chases him through the apartment. “It was our moment to have come fun and do something impressive,” says Nash.

To create the shark, Digital Domain first roughed out a 3D model and then had the model shop sculpt and paint a third-scale maquette. The digital modelers scanned the maquette as a basis for the final 3D model created in Autodesk Maya. “The physical object helped us understand the proportions,” says Nash. “It’s hard to do that kind of modeling on a computer screen. Our shark had a bigger mouth and jaw than any shark of that length would really have.”

Texture painters created sharkskin by painting scars, stressed areas and bite marks into high resolution maps to make the creature look old and dangerous. A custom rig helped animators move the disproportionate hybrid fish on dry land. “That was the trickiest part of animating,” says Nash, “having the shark flop along the floor with some sort of control that gave it weight and kept it believable.”

To help make the shark convincing, animators used a procedural approach to jiggle the shark’s flesh as it bounced on the floor. “When the inertia of the shark changed dramatically – when it lunged forward and then hit the ground – the simulation translated that sudden stop into waves that traveled through the flesh,” says Nash. “We like to use physics whenever we can, because it gives you the most realistic effects.” Although no one has seen a shark slopping through an apartment, people understand how heavy animals should look when they move, he contends.

By rendering separate diffuse, specular and reflection passes, compositors working in Digital Domain’s Nuke could adjust the sharkskin on a per-shot basis. “We could completely control how wet the shark looked shot by shot without having to re-render the element,” says Nash.

On set, the special effects team led by Clay Pinney provided the interaction by breaking windows and closet doors, throwing cushions, and biting the couch using wire poles and pneumatic devices later removed at Digital Domain. A prop house shark gave actors Wilson and Anna Faris something to focus on during the scenes. “They did a great job reacting to something that wouldn’t be in the scenes for months,” says Nash.

In addition to the digital shark, Digital Domain enhanced three meteorites ‘ the G-Girl’s Kryptonite ‘ with 3D elements created in Houdini to make them look self-illuminated and to make electricity dance on the surfaces. One meteorite, a three-foot tall lava rock, emanated CG lightning bolts in a Jacob’s ladder configuration as the rock drained power from G-Girl. “The meteorites were the most difficult work conceptually,” says Nash. “There was no real-world analogy. They could be anything. So we went through many iterations before winding up with an effect that the director [Ivan Reitman] and the studio were happy with.”

Before losing power, however, a digital double of the femme superhero flies through the sky in wide shots, creating a vortex in her wake. “It’s like a heat signature with a cool double helix shape – a disturbance in the air as she flies through it,” says Nash.

A spiral distortion element animated in Houdini created the basis for the vortex. The element itself never appears – the artists used it only to distort the background. The rate at which G-Girl moved through space in a Maya animation determined the speed of the vortex.

“We lined up the 3D element with G-Girl frame by frame,” says Nash. “Then we applied it to the background through Nuke using an image distort mode. It didn’t only distort the background, the color and value of G-Girl streaked into the leading tip of the effect.”

Similarly, when G-Girl moves quickly on the ground, her signature effect trails behind, albeit behind a live action element, not a digital double. “We sped up the background, did frame blending and blurs on Uma [Thurman] in the plate, and use the distortion element in Houdini to affect the background as well as mix in parts of the G-Girl as she moved from A to B quickly.” Rotoscope artists removed Thurman from the plate so that she could move at a different rate than the background. “It was time-consuming work,” says Nash. “The background became a Frankenstein monster of little pieces cut from different parts of the plate to create a clean plate when there wasn’t one.”

The shot count grew from 190 to 300 before settling at 220; all handled by a crew that peaked at around 80. In addition to the CG shots, the crew also composited live-action elements of Thurman shot on bluescreen stages and removed wires from practical effects shots. When a Lincoln town car dropped from a crane onto the street landed at a slant, they straightened it in the plate and added digital dust and debris. All in all, it was a fun project, according to Nash.

“When you’re in the middle of a short post schedule, it can get hectic, and you never have enough weeks,” he says. “But we got to do some fun stuff, and the short schedule means it doesn’t drag on and on.”