The 3DS is really neat. It does do the postcard thing ("parallax barrier"), but only to make sure each eye gets a separate image. It then uses face tracking to

The 3DS is really neat. It does do the postcard thing ("parallax barrier"), but only to make sure each eye gets a separate image. It then uses face tracking to get a much more accurate idea of exactly where the eyes are and renders the image with that in mind, so slightly moving or turning your head adjusts the image appropriately.