Hairy Calculations: Picturing tresses in a truer light

Computer animators find hair tricky to portray realistically because it contains so many strands and because these strands respond in complex ways to light, wind, head motion, and each other. For blond hair in particular, some of the hair’s most important optical properties have been missing from software simulations that render cartoon tresses. So, animators have had to play hairdresser, tediously adding a sunny, diffuse glow to unrealistically dull coiffures.