Feature Film effects: the challenges of creating digital magic for the big screen

Post, Sept, 2002 by Christine Bunish

Thanks to the wizardry of top visual effects houses in the US and UK, moviegoers flocking to the summer's biggest features have been introduced to things they've never seen -- or never want to see -- in real life. From chameleon-like aliens to sword-fighting skeletons, mutant animals, bizarre amusement park rides, an ill-fated nuclear submarine and distant lunar landscapes, audiences have seen digital magic at work.

SPY KIDS 2: A VARIETY SHOW

Swashbuckling skeletons, a miniature zoo, menacing mutant animals and a fantastic amusement park are among the new adventures awaiting siblings Carmen and Juni Cortez, who are back in action in Spy Kids 2: The Island of Lost Dreams.

A new mission takes the kids to a mysterious island where they meet a genetic scientist and his new toy: a tabletop-sized zoo featuring waddling penguins, a hopping kangaroo, a pouncing lion and a lumbering elephant. But in sizing up the miniature animals for older kids to play with, the professor has accidentally unleashed gigantic mutant animals -- bizarre combination creatures whose names reveal their dual origins: tigershark, catfish, horsefly, spidermonkey -- which take control of the island.

Computer Cafe's (www.computercafe.com) Santa Maria, CA, studio devised approximately 16 photo-real 3D animals for about 35 shots, referencing wildlife footage for authenticity. "We tried to keep the animals as anatomically and physically correct as we could down to the details of fur, texturing, color and movement so they would look real and seamless," reports effects supervisor Domenic DiGiorgio.

For the mutant animals, Computer Cafe was challenged to blend the bizarre combinations and not just join two halves of very different creatures, For example, the catfish has both fur and scales with the head of a fish, the body of a normal cat and tail fins. Although the catfish moves like the biggest part of its body, its head and tail have more fishlike motion.

Computer Cafe animators modeled all the animals with NewTek's LightWave 3D using subdivision surfaces. With this technique, the animators could model at very low resolution but render at any resolution desired. Character animation was done with Project Messiah and the beasts' fur, "a traditionally tricky thing," DiGiorgio admits, with Worthy Labs' Sasquatch, a LightWave plug-in and fur shader, which Computer Cafe "pushed to the extent of its abilities."

Under digital effects supervisor David Ebner, the Santa Maria studio composited the zoo and mutant animals' sequences using Eyeon's Digital Fusion as the primary compositing package and 5D's Cyborg for keying many greenscreen elements which, like the entire movie, were shot in 24p HD.

"There is compression in the HD image, so when you pull mattes the blue channel of the video is very noisy making it difficult to get a good key," Ebner explains. "Out of all the compositing packages we have, Cyborg has the best keyer in it." Cyborg allowed the animators to build frames together and play them at HD and full 2K resolution "revealing more detail before we finished out," Ebner says.

About one month from the delivery date of the zoo and mutant animals sequences, director Robert Rodriguez presented Computer Cafe's Santa Monica studio with an additional challenge: approximately 38 shots in which the young sleuths battle swashbuckling skeletons climbing a rocky promontory

Computer Cafe received an animatic of the sword fight done in AliasWavefront Maya, which articulated the skeletons and established the majority of the character animation. The studio had to polish the animation, tweaking and smoothing motion and actions in conjunction with the director's requests.

Daniel Lobe and Robert Bardy hand animated the skeletons in Maya working with Rodriguez on choreography, continuity and timings. "We hand animated 63 characters," reports animation supervisor David Lombardi. Over 28 shots feature multiple skeletons." Jeff Dierstein handled modeling and surfacing.

Radiosity rendering, which calculates bounced lighting, was done in LightWave. "It's uncommon to use radiosity rendering in production," Lombardi notes. Traditional CG rendering is faster, but radiosity rendering is much more accurate and realistic -- especially for an outdoor scene with nooks, crannies and sword reflections -- because it's what happens in nature." Computer Cafe's Ben Grossmann composited the shots using Adobe After Effects.

The studio was also charged with the sequence's wire removals; the kids had been rigged for safety on a dramatic real rock formation as they battled the as-yet-unseen skeletons. Three or four shots were the gnarliest wire removals I've seen," reports Lombardi, "They were tough for even the most experienced artists." The camera moved on three axis changing the 3D perspective on the rocky promontory and making wire removals extremely difficult. For one shot that was crisscrossed with wires, animators rebuilt an entire clean rocky terrain in 3D. It was tracked into the shot with 2d3's Boujou software and composited under the kids. Grossmann did the bulk of the wire removals on Discreet's Commotion with Andy Edwards and Glenn Bennett manning Discreet's Flame.