The Perpetual Diamond: Contrast Reversal Along Edges Create Appearance of Motion | Hacker News Reader

The Perpetual Diamond: Contrast Reversal Along Edges Create Appearance of Motion

journals.sagepub.com

149 pointsmhb35 comments

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I've recreated the illusion in 139 characters* of Javascript: 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.

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.

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.

Can you see the edges between the diamond and the background? Typically, the motion occurs when you can see the edges, and disappears when you are far enough away to make the edges too thin to be seen.

i didn't really find it compelling until the point in the video when they change the direction

This is amazing, Bravo. I found myself fascinated and just staring wondering when that diamond would get to the top.

I wonder if this might be used for loading/waiting transition assets on apps/websites.

Would it appear to be fixed in place if actually moving down the screen?

I don't think so, for me the illusion is not just uniformly upwards throughout the cycle, but also includes a sudden downward shift, so its more like sawtooth motion illusion., so if it were to move down I predict it would look more like a somewhat static diamond jumping down in steps... it would be interesting to try in order to determing the exact illusory motion profile, if it doesnt seem static between the jumps but seems to wiggle up and down before jumping...

Edit: if someone would try this, I would recommend using a larger diamond with thick enough edges and viewed from a distance such that pixelization effects are ruled out...

no, it still appears to move, BUT it can appear to move at angle if the diamond's movement is to the left or right.

Very cool!

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

> 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/

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.

> 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.

There is a large collection of gifs based on the reverse phi illusion in a tiny obscure subreddit that I unfortunately can't find again. I think most of the submissions were made by a handful of users and they never referred to the effect by name. It was mostly artistic applications such as an angel infinitely rising upwards just by flashing two images. If someone finds it again, please let me know!

I too tried to find a few collections I've come across, but no luck... not too sure of what search terms to use. Was hoping someone else would come in clutch.

Here is one that looks like a train coming into a station. https://youtu.be/1dgLEDdFddk

Ha, nice one. I studied that movie in Film History.

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

https://i.imgur.com/4oZyQFx.gif

https://i.imgur.com/2eDISOQ.gif

Epileptics and others with strobe sensitivity: avoid.

It's even worse with the second of these gifs: if I look at it frame by frame, with ample pauses, the scene still keeps rotating in the same direction. I know that two of the four frames must return to the other position, but I can't see it.

Yes! same thing only a minimalists version

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

Arthur Shapiro, one of the authors, has a similiar interactive one here: http://shapirolab.net/P5/Diamond/

That's the most striking visual trick I've ever seen. Surprised it's not used in advertising (yet).

Awesome! It's really hard to not believe that the diamond is moving.

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?

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

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...

It’s not a bad thought:

https://www.sciencealert.com/light-system-stops-motion-sickn...

I would like to see examples too! That would be cool

Could you point to some examples?

I would also be interested to see any examples of this in games, I can't think of any myself.

It's like a visual version of the Shepard tone

https://en.wikipedia.org/wiki/Shepard_tone

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

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