File under impossible objects, this is the Impossible Rooftop Illusion or “Anti-Gravity Two Sided Roof” by Meiji University’s Professor Kokichi Sugihara in 2013. Using computer software, Sugihara creates award-winning, perception-bending 3D models that seem to defy geometry. While the structures look impossible from one angle, viewing them from another angle reveals the illusion. Of the computer-designed impossible motions, he writes:

“Computational illusion” is aimed at studying human visual illusions mathematically. If we could reveal how and under what conditions human visual illusions occur, we would be able to numerically express the strength of visual illusions and control the quantity.

Here’s one more, via Folding Ladder.

Watch related videos about perception and optical illusions. There’s also more of Sugihara’s work in the archives, and the article at The Illusion Machine That Teaches Us How We See.