Simanaitis Says
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THE EYES HAVE IT—0R D0 THℇY?
ARE THESE characters above alphabetical Os or numerical zeroes? Is that a backwards 3 or a stylized alphabetical E, or is it the Greek letter Epsilon or Euler’s constant?
Here are tidbits on optical illusions gleaned from one place or another.
Creative Negative Space. Have you noticed the white arrows on FedEx delivery trucks?
Federal Express was established in 1971, though this latest logo made its debut in 1994 and has received some 40 design awards since then. It’s an example of what’s called “creative use of negative space.”
And I always thought R&T arties were just talking arty talk.
Here’s another example of the potency of negative space. Is this a silhouette of two faces or a vase?
This and the image following are from coopervision.com, October 29, 2014.
In “How Optical Illusions Work,” CooperVision writes, “Sight is a complex process that involves our eyes sending raw information to our brain to interpret. This visual system takes many short cuts and makes edits to images before we’re even made aware of them. Optimal illusions take advantage of these short cuts and use them to fool the brain.”
Tricks of Depth Perception. Also discussed by CooperVision is the Ponzo Illusion of two parallel lines placed over a train track.
The two yellow lines are the same length. The website verywellmind.com, December 9, 2019, cites Italian psychologist Mario Ponzo having demonstrated in 1913 that our sense of depth perception can fool us.
Experimenting With Depth Perception. Back when I was teaching mathematics, I tutored a sightless student. I learned a great deal from this young lady, who, by the way, had also been commissioned to help with Braille signage for a newly constructed subway system.
“Snow,” she taught me, “is the sightless person’s fog.”
One of the things she asked about was sighted people saying objects looked tiny when viewed from far away. We devised an experiment based on Ponzo’s work with converging straws and pencils of different lengths.
We also concocted an acoustic analog: Noise of constant volume diminishes as the source moves away from the listener. Which, by the way, got us both into learning more about the Doppler Effect and its apparent visual kin, the astronomic Red Shift.
Visual Distractions. Many optimal illusions make use of visual overload.
German astrophysicist Johann Karl Friedrich Zöller devised this visual distraction in 1860. Its short segments persuade us to think that the oblique lines are not parallel. Image from VeryWellMind.
One of my favorite visual distractions is from MIT Technology Review, which asked whether these are concentric circles. What do you think?
The magazine discussed optical illusions in light of neural network research and deep learning: “Current machine-learning systems cannot generate their own optical illusions—at least not yet.”
Perspective Foolishness. The Triple Entabulator is part of engineering drawing lore. It’s not so much illusionary as it is pure entertainment.
The Triple Entabulator.
Multiplicity of Views. Optical illusions such as the FedEx arrow are binary, in that either the arrow or the FedEx wording is seen. Here’s a simple drawing that manages to be tertiary. Is it a small box in a corner? A large box with a cubical notch? Or a large box soaring upward to the northwest with a cubical nose pointing off in a southeasterly direction?
To my eye, rotating the image encourages these three perceptions to evolve. (Viewed on a smart phone, temporarily lock its Portrait Orientation.)
All in good visual fun. ds
© Dennis Simanaitis, SimanaitisSays.com, 2020
Simanaitis Says 
I can only manage to see two of the three options on the cube/box.
All this brings to mind Escher’s Convex/Concave [https://www.wikiart.org/en/m-c-escher/convex-and-concave], where the left side is convex, the right is concave and the middle is both, depending on where you start.
Actually looking at the picture again, the convex side has elements of concave, and the concave side elects of convex.
Two other Escher illusions that I enjoy are the infinite waterfall [https://www.wikiart.org/en/m-c-escher/waterfall] and the infinite stair case [https://www.wikiart.org/en/m-c-escher/ascending-descending].
I have three large Escher prints in my family room, the convex/concave, waterfall and day-night [https://www.wikiart.org/en/m-c-escher/day-and-night], where the scene mirror images from day on the left to night at right, and transitions from fields at the bottom to birds at the top.
Agreed. I find the nose a hard one to visualize. This is why I think in directional terms.