Hélio Oiticica (1937–80) was one of the most brilliant Brazilian artists of the 1960s and 1970s. He was a forerunner of participatory art, and his melding of geometric abstraction and bodily engagement has influenced contemporary artists from Cildo Meireles and Ricardo Basbaum to Gabriel Orozco, Dominique Gonzalez-Foerster, and Olafur Eliasson…