Director John Lasseter (left) sees limitations as opportunities and urged truth to materials to supervising td Eben Ostby (center), supervising animator Doug Sweetland and the rest of the team.  

In terms of Lightning McQueen (an homage to the late Pixar animator and car enthusiast Glenn McQueen), they looked more to sports figures than Steve McQueen for inspiration: Tiger Woods, Joe Namath, Muhammad Ali and Michael Jordan. It was important to stress amazing natural talent and tremendous ego. They played up his obnoxiousness and extraordinary flights of fancy in another Miyazaki nod.

“A lot of this came from John,” Sweetland continues. “One of the things he kept talking about was truth to materials, which we were betraying left and right before production. Just don’t bend the cars too much. Obviously we understand their suspension — the undercarriage of the car — so you can have a lot of leeway there as far as making gestures, but this is not a squash-and-stretch show, which is another reason why a lot of animators might’ve thought that their hands had been tied after The Incredibles. Again, it becomes more of a finesse game and you find new solutions or you find that you don’t have to do so much with gestures. In one case, Hud’s bumper is chrome and it’s one of the most highly reflective elements in the movie. And you can see the whole world reflected in this object. The more it bends around, the more it looks like a noodle. It’s a really highly sensitive area. And [in many respects], he’s the emotional center of the movie. We looked at Paul Newman from Color of Money and Nobody’s Fool, and it made sense to keep the bumper pretty immobile because Newman doesn’t move his mouth that much. So he has a certain gravity that he lends to a scene [because of his talent and stature], which satisfied a technical need as well as a creative one. But I don’t know if we would’ve arrived at that decision without this limitation. And John is the first one to say that limitations are opportunities.”

RenderMan was used to create the reflections in the car paint. The accuracy of the reflections was very important and revealed how well the cars are put together.  

Innovative Ray Tracing Was Key
The goal on Cars was to also push the visuals further than ever before, which could not have been achieved without advancing ray tracing at Pixar. “We were essentially early users of the ray tracing capabilities that the RenderMan group has put into the renderer,” Ostby explains. “We used them in a lot of different ways to do three or four primary things that we couldn’t do before or were hard to do. The most obvious thing for car paint is that it needs to have reflections and the accuracy of reflections is very important. For instance, you can see eyes reflecting in a hood. This is a vital cue. Other things that seem subtle show how well a car is put together. An example of that is when you have a shiny chrome trim ring around a headlight, there’s a little bit of reflection back and forth where the ring hits the body and tells you that it’s really sitting on the body and not floating out in front of it. Without those reflections, it doesn’t appear like it’s the same piece.

“Plus, the reflections of the world around the car could’ve been done with older, simpler technologies. But some of the reflections really needed ray tracing. Something else that’s very important in terms of the realistic look that we’re after is ambient occlusion. It’s the way the corner of things get darker, essentially: the little cracks and crevices and areas that have a broad shadow — that’s ambient occlusion, which uses ray tracing to figure out how much of the light coming from all directions impinges on a particular spot. So characters that are not terribly reflective, such as Mater, get a lot from that: it makes them feel richer. Where ambient occlusion is really critical for us is a CG shadow. We noticed that one of the things that made a car feel real in the open sun is that the shadows underneath are inconsistent, they’re not as dark along the edge as in the middle, so we got that with a combination of occlusion and shadowing.”

A further lighting technique used on Cars was radiance, which is primarily the color light spill from one object onto another. When McQueen drives along the racetrack, a reddish puddle of light that’s mixed into the shadow is an example of radiance.