Drive Time
Issue: Volume: 27 Issue: 7 (July 2004)

Drive Time

The CG artists at visual effects boutique Kroma were sitting in the driver's seat while creating three compelling, action-oriented TV commercials for FOX television's NASCAR coverage.

To illustrate just how tough the sport's drivers are, the tongue-in-cheek spots feature famous racecar drivers talking about the dangers athletes in other sports face while they nonchalantly pilot their cars through the mayhem of a NASCAR event. In "Rear-Ended," for instance, driver Tony Stewart states how worried he is about football players and the hits they take—just as his car is struck from behind and spins out of control, and a tire rolls from the vehicle toward the camera.

For the interior scenes of the spot, Stewart was filmed against greenscreen inside a mechanical rig set up to simulate the movement of a car. During postproduction, Kroma's "driving team" integrated those elements with live-action footage and CG effects to make it appear as if Stewart were inside an actual car.
For the FOX TV ad, driver Tony Stewart was filmed against greenscreen in a mechanical car rig (left). Later, CG artists incorporated 3D safety gear and reflections, and added a composited racetrack backdrop.

The artists also added CG safety gear and other digital enhancements, using Softimage's XSI content-creation software, and replaced the greenscreen backgrounds with composited views of the racetrack. In the process, they created a number of details, including a CG visor on the helmet Stewart wore during the shoot. "If you look closely, you can see moving reflections of the track in the visor," notes visual effects supervisor Bert Yukich. "We also added a few hairline scratches to the surface as well, for realism."

For the exterior scenes, director Joseph Kahn from HSI filmed a dozen cars moving around an oval track. Then, Kroma supplemented the real vehicles in post with CG models to create a highly choreographed, tight pack of 30 to 40 cars typical of NASCAR events. To achieve the correct look and motion for the models, the group reviewed hours of actual racing footage provided by FOX.

Yukich also attended the location shoot, gathering reference materials that enabled the group to seamlessly integrate the computer-generated cars into the real environment.

For example, he says, "We shot a number of stills, and gathered [high-dynamic range] lighting data that allowed us to replicate the lighting conditions at the track and apply those to the CG cars."

To enhance the scene, the artists also added smoke and debris to the track environment, as well as the tire that flies off the car, using an Avid|DS editing system.

For one of the more challenging effects, the team included a shot in which the camera moves from an exterior view of the cars whizzing around the track to the interior of Stewart's car. To accomplish this, the artists created an artificial camera move that bridges the two shots and, at the transition point, substituted a CG model for the real racetrack.

As is often the case with realistic visual effects, it's the little things that establish the illusion. For instance, the group added film grain for a live-action look, and introduced camera shake to the shots of the driver to simulate the shimmy effect resulting from a car traveling at top speed.

Recently, Kroma received a Clio Award for the visual effects in "Rear-Ended," earning the boutique a victory lap in the race for innovative digital effects in television commercials.

Karen Moltenbrey is a senior technical editor atComputer Graphics World.