Playing with Stereograms

Stereograms are used to help visualize mathematical objects and constructions.  This stereogram applet is very large, so it opens in another browser window.  Click your web browser's "Back" button to return to this page.

Click here for the stereogram applet.

What is a stereogram?  A stereogram is a two dimensional (flat) picture which, if viewed properly, gives the impression of three dimensional (3D) space.  A stereogram uses the same principles as our eyes do to get a 3D impression of an object.  For example, when you look at a tree, it doesn't appear to be flat, but appears to have depth within the space in which it stands -- it's 3D.  Looking at a tree, two pictures appear on the retina of your eyes, one picture on each eye.  Each picture is two-dimensional, but the tree looks like its actual 3D reality.  This phenemon happens because the two pictures on your eyes aren't identical.  The difference in the pictures is caused by the placement of our eyes.  An adult has approximately 7 cm between the eyes.  If you're looking at an object ten feet away, for example, the direction of our eyes isn't parallel, but is actually at an angle.  The angle depends on a distance of the point we're viewing.  Only as we look towards infinity will the direction of our eyes become parallel.  The angle between the direction of our eyes is crucial for 3D perception.  The stereogram measures these angles for you.

To view the stereogram applet, focus behind the picture to make the angle smaller than the one you get if you focus on the picture itself.  If you keep focusing behind the picture, the points on the stereogram will start to fuse - and you'll see the 3D impression of the image.  Enjoy!

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Thanks to Borut Jurcic Zlobec for the Stereogram applet.

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