Prof. Kokichi Sugihara – optical illusion engineer (#70)


Kokichi Sugihara is a Meiji University distinguished professor emeritus as well as a professor emeritus of the University of Tokyo. His research area is mathematical engineering. In his research on computer vision, he found a method for constructing 3D objects from “impossible figures,” and extended his research interest to human vision and optical illusion. Constructing mathematical models of human vision systems, he created various new impossible objects, and won the first prize three times (2010, 2013 and 2018) and the second prize twice (2015 and 2016) in the Best Illusion of the Year Contest. 

What have you discovered recently that either surprised you or made you go “Wow”?

A heart mark formed by liquid in a special cup. It was served as an appetizer for a
dinner at a hot-spring hotel in a small mountain area in Japan, named Ginzan Onsen.


Can you tell me about your career from a mathematical engineer to award-winning optical illusion designer?

When I was young, I did research into computer vision, and one of my problems was to reconstruct 3D structures from 2D pictures. At that time I found an equation that represents the set of all possible 3D structures whose projections match a given picture. Using this equation, I found some “impossible figures” are not impossible, and extended my research interest to human vision and optical illusions. Using my equation, I constructed a mathematical model of the human vision system; I am still improving this model. My main inspiration to create new 3D illusions is based on this model. This model makes me able to predict what the human vision perceives when new 3D objects are shown. So I can search for objects whose perceived shapes are very different from the true shapes. This is my way to find new illusions.

The artist M. C. Escher has also inspired my work.  He represented various impossible worlds by 2D pictures, which stimulated me to create 3D versions of impossible worlds.




What is the appeal of creating impossible motion and ambiguous solid illusions?

It is a great fun to create new types of 3D illusions myself, to show them to others and to surprise others. I am just enjoying myself with these research activities. As by products, those illusions show some psychological natures of our brains: our brains seem to prefer rectangular structure when interpreting 2D pictures; our brains ignore our knowledge about the true shape of the objects when interpreting  2D pictures (i.e., even after we understand the true shape of the object, we have the illusion again when we go back to the special viewpoint); some illusions are very strong so that binocular stereo does not work (i.e., some of illusions occur even we see the objects by our two eyes at a short distance.)


Does all your work with illusions cause you to doubt your own senses?

Yes, I experience the illusions myself. I cannot correct my visual perception although I have been investigating those objects for more than 40 years. I believe that if I could correct my brain so that I could not see these illusions, I would have trouble in my daily life. This is because the nature of our vision system that has illusions is useful in ordinary lives.


Do you have a favourite illusion that you’ve created? Why was this?

An arrow that likes to face rightward. This is because the illusion is very strong. The illusion occurs even if we see this object by our two eyes at a short distance. (Many of my illusion objects only work when we see them with a single eye or when we see a photograph.)


I think you’re now on your 9th generation of impossible objects, how far do you think we can push our perception of reality?

I feel there must still be many other types of 3D objects whose behaviours appear to be impossible. I have concrete ideas about at least four more, although each requires a lot of time to develop computer programs for creation.


Has the invention of the 3D printer made a big difference to your work and what illusions can be made? And how does it feel to have your work being reproduced by 3D printers across the world?

Yes, definitely. In the early days, I made my computer draw the unfolded surfaces of the
computed objects and made paper models by cutting and gluing. So, I could make only
planar-face objects. Since 3D printers became available, I can design objects with curved
faces, and so the freedom in the design of illusion objects has been extended.

I am happy to learn that there are people who are interested in my illusions and who try
to experience the illusions themselves by reproducing the objects using 3D printers.

Matt notes… Inspired by these illusions I came up with a simple ambiguous solid made from a cardboard tube. See the video below of how to make you’re own.

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