Docter began working on the story in 2004, which was based on fantasies of escaping from life when it becomes too irritating. He and eleven other Pixar artists spent three days in Venezuela gathering research and inspiration. The designs of the characters were caricatured and stylized considerably, and animators were challenged with creating realistic cloth. The floating house is attached by a varying number between 10,000 and 20,000 balloons in the film's sequences. Up was Pixar's first film to be presented in Disney Digital 3-D.