First, understanding that these two explosion effects needed a high level of detail, which would need to generate a huge amount of particles, Geiger began a couple weeks of research and development with professor Ron Fedkiw of Stanford University. They worked toward generating a fluid solver to avoid the memory usage problems inherent with using massive amounts of particles to hammer out the motion of the explosion itself. They came up with a 2D fluid simulation method that provided them with almost realtime feedback for the explosion’s motion. This enabled the small effects team to design the flow of the explosion with a hands-on approach to get their desired result.

Geiger exported the fluid motion data in slices into Maya’s particle engine to use as velocity fields with which to move Maya particles for better visualization. The slices of fluid data made it much easier to create the particle motion that they used to visualize the explosion. The explosion was then rendered through a custom volumetric raytracing renderer written by Geiger for Star Wars Episode II.

The first shot was then composited together with animated volumetric cloud rings moving out from the epicenter, as well as a wicked shockwave that rips through the city in the overhead shot of the first explosion. An ILM proprietary desktop node-based compositing system was used to pull the elements together for the first explosion shot in the city in the dream sequence, and an Inferno system for the subsequent explosion of a fuel cell later in the movie as John Conner and the Terminator are traveling through the desert. The same animation procedures were used for that smaller explosion as well.

T3 explodes on the big screen with some of the most stellar CG explosions ever made.

Interestingly enough, all the renders where output into different lighting passes using the three inherent color channels of the image files. The key light used on the explosions was output through the red channel, the bounce light through the green channel and the self-illumination glow of the explosion through the blue channel. This gave the compositor greater color and image control over the composite all from within a single output.

Two additional animators were brought in to add some ancillary details to both scenes in the last two weeks of the production period. But for the most part, Geiger and a single compositor worked through the short 10-week process from R&D to completion to produce these two shots. Quite a nice accomplishment, since the effect was right on the money. And the rest of the film’s effects clearly keep up the same standard set by these initial effects shots, though theey were clearly my personal favorites. Props to the peeps.

Dariush Derakhshani is an early 31 and makes for an interesting Googlism. Nicely bald and slowly going insane, he has a fear of commitment and of having to cook. He has written a bunch of articles littered about the Web, wrote for Maya: Secrets of the Pros and Maya 4.5 Savvy, is writing his own Maya book due out this SIGGRAPH, and co-moderates the 3d Hardware List e-mail forum (www.reiss-studio.com/3dhardware to join). A senior animator at Sight Effects in Venice, California, he can be found at www.painfulurination.com or you can send him viruses at koosh3d@earthlink.net. He's got flat feet.