For the technical crew members, the film's human characters posed a difficult set of challenges. Bird's story was filled with elements that were difficult to animate with CGI back then. Humans are widely considered to be the most difficult things to execute in animation. Pixar's animators filmed themselves walking to better grasp proper human motion. Creating an all-human cast required creating new technology to animate detailed human anatomy, clothing, and realistic skin and hair. Although the technical team had some experience with hair and cloth in Monsters, Inc. (2001), the amount of hair and cloth required for The Incredibles had never been done by Pixar up until this point. Moreover, Bird would tolerate no compromises for the sake of technical simplicity. Where the technical team on Monsters, Inc. had persuaded director Pete Docter to accept pigtails on Boo to make her hair easier to animate, the character Violet had to have long hair that obscured her face; in fact, this was integral to her character. Violet's long hair, which was extremely difficult to animate, was only successfully animated toward the end of production. In addition, animators had to adapt to having hair both underwater and blowing through the wind. Disney was initially reluctant to make the film because of these issues, thinking that a live-action film would be preferable, but Lasseter denied this.
