Computer Graphics World

May 2009 24 n n n n Lights•Shaders tions—a bridge over the Rio Grande Gorge near Taos, New Mexico, a partial bridge set in Albuquerque, New Mexico, surrounded by red dirt, and a flat road—and then flew Hunter-Killers down the digital gorge and added practical explosions, actors shot on wires, and the harvester. Still another sequence begins in Albu- querque on location, moves into the backlot for shots of a helicopter against bluescreen, and then back outside. ILM added minia- ture satellite dishes from Kerner Optical to the real backgrounds, and miniature back- grounds to the bluescreen footage. e artists cut from a real helicopter to a CG helicopter, and from Christian Bale to a stunt actor and back to Christian Bale, and they added digital elements, including a nuclear explosion to the background, to create the aftermath of a war. One sequence takes place in the wreck- age of San Francisco where, after the judg- ment-day war, Skynet built the manufac- turing plants and refineries it needed for its processing center and bulldozed through the rest. "e conceit is that there is a lot of com- puting power in San Francisco," Snow says. "We even made jokes about putting it here at ILM because we have so much compute power. But, we ended up moving it down- town to give John Connor a longer jour- ney." e shot starts with Christian Bale riding a proxy Moto-Terminator filmed from a helicopter. ILM removed that bike, put him onto the beefed-up CG Moto-Ter- minator, blended to a digital double, then pulled back to reveal a digimatte painting of Skynet. "ese sorts of shots have precedence in things like the big, long shots you've seen in Children of Men and some of Bri- an De Palma's work," Snow says. "But, those are always intensely choreographed with a week of rehearsal and then shot all in one. We're trying to give that impres- sion, but with many disparate elements. It's complicated to do. We're using every one of the tools we like to group together and call D-Cinema—layout tools, roto- scoping tools, and the ability to reproject plates onto one another." And to create the look, the energy-preserving shaders and HDRI. High Contrast "e new shaders were important to be able to match the real puppets on set," Snow says, "but also to cope with the harsh look of the film. McG and [director of photography] Shane Hurlbut wanted this extreme look where the black levels go to hell and the highlights are beyond some of the dynamic range that we could cope with until a few years ago. So com- bining our energy-preserving shaders with HDRIs protected us in the harsh desert environment where the sun is many stops higher than the shadow side." On set, the ILM crew captured HDR images using five exposures three stops apart every time the lighting in the envi- ronment changed, as well as stills for photo- modeling the environments and shots of the chrome and gray spheres. "I like to have the chrome and gray spheres be- cause they pin down the lighting when you shoot the plate," Snow says. "And because we scan them, they give me something to color-match the HDRIs to. Also, it's our only way to capture really dynamic light- ing environments like the explosions and sparks in the factory scenes. We're looking into ways to capture dynamic lighting as HDRI data, but we didn't have anything ready for this film." To be certain final shots would hold up after DI, Snow had ILM create two versions of each and sent both versions to McG: the neutral version they worked with in produc- tion, and a DI proxy version that matched the super-high contrast, desaturated look that McG and Hurlbut wanted. "We knew going in it would be harsh, so we used the more energy-conserving shad- ers and higher dynamic range images in our look development," Snow says. "And in compositing, we created the two looks. e neutral grade gave them maximum flexibility, and the DI proxy showed that our black levels were robust enough to hold up. So, the shots dropped right in, and we've had no kickbacks from DI. It's the first time we haven't had to go back and redo some shots." Each year, as tools become more sophisti- cated and compute power increases, CG art- ists have the opportunity to experiment with the art of visual effects in new ways. e look of this film and the kind of visual effects it incorporates provide a dramatic example of just how far the industry has come. n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. The giant, headless terminator shooting from behind the building is a CG harvester. It houses the Moto-Terminators, which race out from inside its legs to round up humans.

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