Movie studios often want computer-generated hair to have a specific effect, whether it's a seductive toss or a careless flick that knocks something over. But there's a problem: most rough-cut simulations don't realistically simulate hair, leading to a lot of guesswork and time-consuming edits. Disney (no stranger to hair-centric movies) has a solution, though. It developed a new system that can produce more authentic-looking simulations without an impractical boost to computation power. The trick, it turns out, was to use just a few cleverly controlled sample hairs.