When I was a teenager, Magic Eye pictures were all the rage. You would stare at an abstract collection of simple shapes and patterns, and, if you were lucky, a 3D picture of a unicorn or a baseball player would suddenly appear before your eyes. Some days, it would be easy; other days, I would stare for near an hour at one picture, but the 3D image would fail to reveal itself. And some of my friends could never get the image to pop at all – the joy of these magical reveals was lost on them completely.
But how do these pictures work?
These images, officially called stereograms, play an interesting trick on your brain and eyes. As your eyes look at the picture, they will settle on two different spots. But because the pattern is small and repeating, your brain is fooled into believing that there is but one spot; your brain thinks your eyes are looking at the same point. Of course, this assumes that you don’t have one eye significantly more dominant than the other; your eyes have to work as a coordinated team in order for you to see the hidden image, so if you can’t, it might be a good time for a checkup at the eye doctor.
When your eyes work together while looking at the picture, the brain perceives the two points to be on a virtual plane behind the repeating pattern, giving shape to the 3-dimensional image hidden within. The hidden image is created in gray scale, and your eyes perceive depth which is not there, making the image appear 3D, by making closer points light, and receding points darker. The pattern is overlaid, with a specific algorithm, allowing the pattern to create the depth and dimension that you perceive the hidden object to contain.
Make sense? Yeah, I don’t get it either. But they sure are cool!