A pencil tip moves across a sheet of paper, leaving a thin graphite line. Perhaps a millimeter across, it could be swiftly erased. Or it could become the spark for the greatest performance cars that have ever existed: perhaps Marcello Gandini's 1966 Lamborghini Miura. Or Jean Bugatti's 1937 Type 57 SC Atlantic Coupe. Very different designs, but both born of a mere line arcing across paper. For Alex Shen, studio chief designer at Toyota's Calty Design Research in Newport Beach, California, the words describing the sports car's styling concept came first -- words like "sexy," "honest," "organic," "kick-ass." Followed by proportions -- front/mid-engine, rear drive, just the right scale. And a wild guess at price -- maybe $60,000? "It's a Toyota," says Shen. "It ought to be affordable." Only then did lines start to appear. But when they did, it was an avalanche. Virtually every designer in the 65-person studi...