Issue link: https://digital.copcomm.com/i/77744
VFX•CG Films n n n n the laser slices her. Then the spreaders come in to open her stomach, and a giant claw comes down and pulls out a baby trilobite." The baby trilobite was a practical puppet that, while in the placental sac, didn't move. "When you see it twitching in the sac, that's our shot," Hill says. "You can see embryonic goo and strings of viscera connecting it back to the stomach." around wildly. "We did some of the more pre- cise motion, but it was also practical. About half digital, half practical," Hill says. "The goo that splats back onto the stomach was practi- cal. But, we had a lot of simulation for fluids dripping off that had to match what was on set precisely because this is in stereo. So, we did a lot of re-projection onto models, some CG work, and Alfred Murrle's team did some very good comp work for the sequence." The shot doesn't end there. "The really gro- tesque part is of her becoming stitched back up," Hill says. "We knew they wanted a sta- pler; they had put enormous staples in her on set. We needed to make a machine that felt solid enough to punch those staples. We looked at jackhammers and pneumatic road When the sac bursts, the trilobite thrashes drills for motion reference. Whenever the sta- pler punches in, we have it punch two or three centimeters and create deformations around that. It's quite brutal." A Trilobite Fight Despite the complexity of these two se- quences, Hill points to shots of a fight be- tween the last engineer (actor Ian Whyte) and a trilobite as the most difficult. "As an adult, the thing that came out of [Rapace] is 14 feet across from tentacle to tentacle," Hill says. "When the engineer and trilobite fight, Noomi [Rapace] is caught in the middle. These shots were the hardest because they lit everything in a strobe envi- ronment. No frame was the same as the one before. And, Ridley wanted to catch it all in camera. They had Ian Whyte all wired up and fighting against air where the trilobite would be. We had to matchmove him perfectly to give animators something to work with and to position the digital trilobite. We had to re- place a limb on the engineer in some shots, and we needed tight tracking for the creature rigs. Tracking software doesn't respond well to incoherent flashing light." On set, the crew had three reference cam- eras and a main camera to help provide an accurate representation of the action to help animators, lighters, and rendering artists fit the creature into the shots. "The trilobite is very deformable," Hill says. "It has six or seven tentacles wrapping and constantly moving in this strobing environment, and one tentacle compresses against the en- gineer's limbs and body. So on top of the muscle model our creature team used, we needed an extra simulation layer. We used a cloth simulation to produce the longitudi- nal wrinkles on the trilobite, and then com- pressed them around the axis of the tentacle. We passed all this information to the shad- ers so the skin would become shiny when tense and rougher when compressed." All told, approximately 350 people at Weta Digital worked on the studio's 250 shots. "It was hard," Hill says, "but the whole team was elated to be working on such an iconic piece of cinema." n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. (Top) The fight between the last engineer (actor Ian Whyte) and the trilobite was the most difficult for the artists at Weta Digital. (Bottom) Matchmovers tracked the actor in an environment lit with strobe lights (left) to replace body parts digitally (middle) and insert the digital trilobite (right). June/July 2012 51