
The Perpetual Diamond: Contrast Reversal Along Edges Create Appearance of Motion - mhb
https://journals.sagepub.com/doi/full/10.1177/2041669518815708
======
twiceaday
I've recreated the illusion in 139 characters* of Javascript:
[https://www.dwitter.net/d/14459](https://www.dwitter.net/d/14459)

* Dwitter has a built-in `R` for RGB color, `S` for Math.sin, and `x` for the 2d context of the canvas.

~~~
hammerbrostime
Does anyone else _not_ perceive motion in this?

I can see the background color oscillating, but the foreground figure remains
stationary. Viewing it on an iPhone.

~~~
tsukikage
Perhaps the iPhone is scaling the image down so much you lose the thin outline
around the foreground figure?

Try on a tablet or desktop.

------
soulofmischief
I've seen the reverse phi illusion effect crop up a few times in various
places. [0] But as the paper says, it typically involved changing the
luminance of the foreground object.

It's cool to get a breakdown of exactly what makes this effect tick.

Are there any other good non-static optical illusions such as this? As in
illusions which require some element that changes over time cyclically in
order to produce the effect?

[0] [https://michaelbach.de/ot/mot-
reversePhi/index.html](https://michaelbach.de/ot/mot-reversePhi/index.html)

~~~
panic
_> Are there any other good non-static optical illusions such as this? As in
illusions which require some element that changes over time cyclically in
order to produce the effect?_

Here's one which uses the surrounding color to make synchronized flashes look
like alternating flashes: [http://illusionscience.com/contrast-
asynchrony/](http://illusionscience.com/contrast-asynchrony/)

~~~
ehnto
That is excellent. I developed a trick when playing piano where I can roughly
count two things at once for a short period of time (Any Murakami fans? Hard
Boiled Egg and the End of the World made me try it!).

When I tried to do that to count the flashes the one I was looking at felt
like it sped up to match the other one but I couldn't count both at once. My
brain was well and truly tricked.

~~~
soulofmischief
> I developed a trick when playing piano where I can roughly count two things
> at once for a short period of time.

Something tells me that developing this skill could be greatly aided by an
interactive visualization. That's something I might look into.

------
aasasd
So I guess this is the trick behind those trippy gifs.

[https://i.imgur.com/4oZyQFx.gif](https://i.imgur.com/4oZyQFx.gif)

[https://i.imgur.com/2eDISOQ.gif](https://i.imgur.com/2eDISOQ.gif)

~~~
dredmorbius
Epileptics and others with strobe sensitivity: avoid.

------
Zanni
That's a really powerful effect. Is there a direct link to the demo somewhere?
I only see embedded videos, even in the PDF.

~~~
mxfh
Arthur Shapiro, one of the authors, has a similiar interactive one here:
[http://shapirolab.net/P5/Diamond/](http://shapirolab.net/P5/Diamond/)

~~~
romwell
Awesome! It's really hard to _not_ believe that the diamond is moving.

~~~
lopmotr
It might be fair to say that it _is_ moving but also staying in the same
position, as mentioned at the end of the article. To say it's not moving is
like saying an animated sprite in a video game isn't moving either - sprite
movement is just an "illusion" of continuous motion rather than the discrete
appearance and disappearance of separate images that it really is.

I wonder if when film or flipbooks were first invented, people considered them
to be an optical illusion too?

------
DiabloD3
Dear God, I remember tricks like these being used in 8 bit era games.

~~~
taneq
I wonder if there's any application for them in VR to counter motion sickness?
Instead of a stationary object looking like it's moving, you have a moving
field of view looking like it's stationary...

~~~
mensetmanusman
It’s not a bad thought:

[https://www.sciencealert.com/light-system-stops-motion-
sickn...](https://www.sciencealert.com/light-system-stops-motion-sickness-in-
self-driving-cars)

------
ot
It's like a visual version of the Shepard tone

[https://en.wikipedia.org/wiki/Shepard_tone](https://en.wikipedia.org/wiki/Shepard_tone)

------
vcdimension
Looks like the sort of thing you see at the early stages of a magic mushrooms
or LSD trip.

