Illusion knitting can be used to create some interesting colour effects. These two panels (which could also be used as cushions) look exactly the same when viewed from the side but very different when seen from directly in front. From the side they both show triangles; from in front one has diagonal lines while the other has squares.
Each panel is about 40 cm (16") square when knitted in DK yarn. You can use any yarn though a thicker, or thinner, yarn might change the overall size. You will need approximately 130 metres (140 yards) of the background colour, for each panel, and small amounts of eight other colours.
Warning: these cushions are more difficult to make than our seemingly complex illusion pictures. You must be used to handling several balls of yarn in the same way that you would work intarsia.