Issue link: https://digital.copcomm.com/i/77744
VFX•CG Films n n n n reform into a recognizable DNA, one found on Earth, with cells that form and split. "Ridley referenced the statue of David in the design of the engineer," Stammers says. "He wanted godlike, alabaster skin with translucen- cy. Weta did a fantastic job of matching the live- action actor." An actor slathered with silicone. Weta artists began by referencing a sculpted maquette that Scott had placed in a lazy Susan, lit, and fi lmed in 2010. "Ridley asked us if we could match it," Hill says. "We applied shad- ers and lit it to match, and when we got to the point where we were happy with that, we added a facial system." Th e digital head they sent back to Scott rotated once, and then on the second turn, it blinked and formed an expression. "Th at brought the head to life and gave Ridley the confi dence that we could create a digital engineer," Hill says. Th ere would always be a point at which the engineer would become digital, of course. Th e question was when. "Th e original plan was to see if we could apply the early stages of the disintegration eff ect to plates of the engineer," Hill says. "It turned out that we have two shots with the eff ects starting on the digital actor. Th e rest is fully digital." Th e advantage in starting with the actor wearing the prosthetic was that the animators had a performance they could match. Th at was also the disadvantage. "Obviously, if you (Top) The engineer begins to dissolve into particulate matter, thanks to the artists at Weta Digital. (Bottom, left to right) The artists directed shaders with fi lmed footage of liquid pumped through blocks of silicone. The alien double helix started as spine bones from a fi sh. Particle simulations drove cell mitosis. have a guy in a loin cloth wearing a silicone suit, his muscles don't fi re and deform like real muscles," Hill says. "We wanted to put in a full muscle, fat, and fascia system, and have all the sliding and tensing of skin to make every- thing physically correct. But, it didn't match the prosthetic. We had to make our digital model less accurate than we usually make crea- tures, and more accurate with the prosthetic." Th at was true for the engineer's skin, as well. Th e silicone was so thick that instead of scattering rays a centimeter beneath the sur- face, the artists needed to reset their subsur- face scattering system to plummet six or seven centimeters deep. "His fi ngers felt like wax, though," Hill says. "We had to include inter- nal blockers to make him look substantial and not like a block of silicone." Re-engineering a Life To create the eff ect of the engineer disinte- grating, the artists once again took the lead from Scott's emphasis on practical eff ects and looked for ways to incorporate real-world ele- ments into the process. "We carved veins into blocks of silicone," Hill says. "We pumped ink and oil, and all sorts of liquid combina- tions through the veins, backlit the blocks, and fi lmed them. We also shot drying clay, drying paint, and other practical elements." Th e shading artists didn't use these practi- cal elements directly. Instead, the elements became drivers for shaders and textures that they applied to the engineer; that is, shaders procedurally driven by practical eff ects. "It was quicker to give blood pulsing and cracks forming a more natural motion by using real elements, so we decided to use fi lmed footage to drive shaders," Hill says. "We heavily processed the images, some of which we fi lmed at high speed, through [Th e Foundry's] Nuke. Some shaders were proce- dural. Some used painted maps. And some included this natural motion to assist the shaders. We'd augment the footage in diff er- ent ways, and it became information maps for diff erent eff ects and stages of the disinte- gration. For example, we took a fi lmed vein pattern and applied it to the skin with a time delay to create bruising. We had veins that became darker and shinier as they popped out: As the skin became taut, the specular would increase, and as the skin dried out, it would become more leathery with lower subsurface depth and aff ected displacement. Th e main thing was to keep the natural mo- June/July 2012 49 Images ©2012 Twentieth Century Fox Film Corp.