Powerful results can materialize by blending computer animation, visual effects, miniatures, matte paintings, and live action. Using this formula, digital artists at Riot (Los Angeles) conjured up a trio of tornadoes that devastates a stretch of farmland in the season-ending episode of Smallville, which re-aired in September.
The tornado sequence occurs after Lana Lang, a friend of the Kansas teenager who would one day become Superman, drives her pickup truck off the road. At first she is awestruck to see three thin tornadoes twisting across nearby farmland. But awe quickly turns to fear as the clouds converge and become one single, mammoth mass of wind and debris. Lang retreats to her vehicle just as young Clark Kent appears. As the storm lifts the truck into the air, Kent rescues her.
Ironically, rain dampened most of the season's shooting schedule, but on the day of the tornado shoot, it was warm and sunny. To create the illusion of dark, stormy skies, the digital artists used Discreet's inferno to replace the blue skies and soft cumulus clouds that appear in the raw production footage with menacing thunder clouds. "We also darkened the rest of the footage, replaced shadows, and adjusted the lighting to make it consistent with the violence suggested by the wind machines used on location," says Don Greenberg, Riot's supervising visual effects compositor.
Greenberg then provided keyframes of the sky-altered background plates to the animators, who generated the 3D tornadoes. "The combined storm had to feel enormous," says John Decker, lead animator. "It had to be a slow-moving, heavy mass." The team gathered images of tornadoes from feature films and documentaries to use for reference but found that the twisters vary in their character. "No two look the same," he points out.
Using Alias|Wavefront's Maya and Pixar Animation Studios' RenderMan, the team at Riot generated all the twisters, then composited them into the live action using inferno. At first, particles were used to make digital dust and debris, then texture maps were added to provide the dense core.
Creating the massive single tornado presented the biggest challenge because it needed to appear both larger and more powerful than the others, and it would be shown in close-up shots. This was done by generating more than 20 layers of particles to create the funnel cloud, then adding numerous 2D and 3D elements to the scene, such as leaves being whipped along the road, swirling dust clouds, and damaged road signs.
To integrate the tornadoes into the background, the team blended the tops of the funnel clouds into the sky and created mattes of foreground elements using inferno. —Karen Moltenbrey
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| Riot artists created a trio of tornadoes that converge into a super-size twister in the TV series Smallville. |