Ran. Illustrations by Akira Kurosawa. Screenplay by Akira Kurosawa, Hideo Oguni, Ide Masato, translated by Tadashi Shisido. Boston & London: Shambhala. 110 pp. $19.95. Before he became involved in the cinema, Japan's Akira Kurosawa had intended to be a painter. In his brief headnote to this striking book containing the screenplay and storyboards of his epic, Academy Award-winning film ``Ran,'' Kurosawa notes, ``when I tried to paint well, I could only produce mediocre pictures. But when I concentrated on delineating the ideas for my films, I unconsciously produced works that people find interesting.'' Notwithstanding the role his success as a filmmaker may have played in drawing attention to his paintings, these beautiful storyboards testify eloquently to his suggestion that expressing ideas is what energizes art.