To prepare this figure, called an anaglyph, Bela Julesz begins by constructing two arrays of randomly placed tiny triangular dots, identical except that (1) one consists of red dots on a white background and the other of green dots on a white background, and (2) over a large triangular region, near the center of the array, all the dots in the grecn-and-whitc array are displaced slightly to the left, relative to the corresponding red and white dots. The two arrays are now superimposed with a slight offset, so that the dots themselves do not quite su-
perimpose