Layer by layer: digital artists make the impossible look real in The Core's inner-earth sequence. (Film).

Usually, realism is the overriding goal of artists creating digital effects sequences for live-action films. For some projects, however, it doesn't make sense to strive for realism when the result will be visually uninteresting. In such situations, artists must achieve a delicate balance between what's realistic and what's engaging to make the shots work.

Such was the case for the effects artists at CIS Hollywood who worked on Paramount Pictures' The Core. In the live-action film, geophysicist Dr. Josh Keyes (Aaron Eckhart) discovers that an unknown force has made the earth's inner core stop rotating, causing the planet's magnetic field and atmosphere In deteriorate. To resolve the crisis, Keyes and a team of scientists journey down through the layers of the planet's interior in a subterranean craft piloted by "terranauts" (Hilary Swank, Bruce Greenwood) to detonate a device that will reactivate the core. CIS was responsible for creating the approximately so-shot digital sequence in which the CG craft, dubbed Virgil, plows through earth's crust, mantle, and outer core, then sets off the explosion, travels back up, layer by layer from the center of the earth, and emerges from the ocean floor.

Art Meets Science

According to Bryan Hirota, CIS visual effects supervisor, the greatest challenge of this sequence involved making it look real, despite the fact that in reality it would be impossible to see any type of craft pushing through rock, lava, silicate compounds, and other elements. "If you were to try and show what a craft like Virgil would look like cutting through the earth's layers, you'd end up with a sequence showing lots of rock, lava. debris, and gases flying around, but not much else," Hirota says.

To accomplish the sequence, the team first turned to tools that would enable them to create scientifically accurate effects. "We based the animation--of the rock in the crust, the lava in the mantle, and what we call the hyperfluid, which is the super-compressed, super-hot solution of liquid and gas in the outer core--on physics and computational fluid dynamics," Hirota says. "We then took liberties in terms of visually telling a story that under normal circumstances can't be told, and of presenting it in a way that would be easily understood by audiences."

A team of about two dozen CIS artists and compositors had approximately eight months to complete the sequence. A portion of the work involved designing and building Virgil, the 150-foot-long, cigar-shaped craft that pulverizes everything it comes into contact with as it descends toward the core. To create and texture the model, artists used Alias|Wavefront's Maya and Interactive Effects' Amazon Paint. For rendering, they used Entropy, a RenderMan-compliant renderer developed by Exluna. (Exluna recently merged with Nvidia and no longer markets Entropy or its other flagship product, Blue Moon Rendering Tools, but is continuing to support existing customers.)

The team spent most of its time creating the different layers of earth and animating the craft smashing through ...