Single Image Random Dot (SIRDS) are not only a lot of fun, but they demonstrate many of the properties of stereopsis. "Stereopsis" means that each eye sees a slightly different image, also known as three dimensional or 3D. Stereopsis is essential for our perception of depth. Leonardo da Vinci demonstrated in his writings that he understood stereopsis, but the 19th century British physicist Charles Wheatstone is usually credited with its first clear demonstration. Wheatstone invented a stereoscope, a device which presented the first . The fir ....