The Impossible Cylinder is a new model we recently made in our workshop and added to our Math Rooms and exhibits.  It has been well received by people of various ages, which we love and think makes for a fun addition to our spaces.

The impossible cylinder illusion, also known as the Ambiguous Cylinder Illusion, works by tricking the brain into seeing a specially contoured shape as either a square or a circle, depending on the viewing direction. 

The 3d printed part is designed with curved top surfaces, two of which curve upward and two of which curve downward. It is placed square on the wooden base of the model, which has an etch to help guide placement of the 3d printed object. The wooden base also holds a piece of mirrored acrylic upright. When viewed from above at a 45º angle, the shape appears to be either a square or a circle, depending on the direction it is facing in the mirror. View from one direction at 45º, and then view from the other direction at 45º. Note the difference in shapes that you perceive. 

What is happening? 

The brain misinterprets the top surface as flat, and adjusts its perception accordingly. The direct views of the model and its mirror image create different interpretations of the 3D shape. The edges of the shape force the brain to “complete” the shape of a square and a circle, alternatively, when the object is rotated. You can learn and play with this model in our Math Rooms, or you can make your own!

Files for this model will be posted here soon.