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Double-mirror illusion (journalofillusion.net)
118 points by weird_user on Dec 15, 2023 | hide | past | favorite | 46 comments


For anyone who's confused about where to find the images: Click "Figures" in the sidebar on the right.

For anyone who's confused about how this works: The objects aren't what they appear to be from any angle. In fact, they're weird mirror symmetric objects that bend backwards in ways you wouldn't expect. It's our shape recognition that makes them look flatter than they are. This also makes them look like asymmetric objects that are facing a certain direction depending on the viewing angle, and this is the actual illusion.

It's sad that we don't get a 360 degree view, or even a couple of rotations of one of these, because that would make it obvious that the object goes from "proper shape" to "unrecognizable shape" to "flipped shape" depending on angle.

Anyway, when viewed in the mirror from certain angles, first of all the object doesn't change (because it's mirror symmetric). But because you view the mirror image from a different angle, it looks as if it's facing the other direction.


This page presents Sugihara’s earlier work and provides 360 degree view:

https://www.sciencebuddies.org/science-fair-projects/project...


What sidebar? I don't see a sidebar. When I click the figures the site just hijacks my browser history.

I think it's about time companies hire the mentally challenged to be front-end devs. I commend the site for breaking new ground in equity.


You need to hold your phone up to a mirror to see it.


If I force desktop view on mobile the sidebar appears


Rotating phone to landscape worked for me.

Desktop mode showed me the same content on my device.


> For anyone who's confused about where to find the images: Click "Figures" in the sidebar on the right.

Thank you! Here's a link: https://journalofillusion.net/index.php/joi/article/view/983...


I suppose it only works on camera. I can't imagine it works in person.


It works only from the forced perspective angle. If you move the camera, the image morphs.


The article has a whole section "Robustness against changes in viewpoint" where it argues that it's good.


Also you have to hold your phone sideways to see the sidebar.


Please, for the love of god, stop with the custom scroll bars, and on the wrong side of the viewport, no less!


Yeah, this might be one of the worst websites I've seen. This is really unenjoyable to navigate.


Is it intentional for some form of irony?


The rationalisation appears to be that there are two viewports, one left, one (when expanding sidebar items) right.

The left-hand scrollbar controls and reports on the left-hand viewport. The right-hand scrollbar the right-hand viewport.

More conventional organisation (and less confusing, possibly) would be to retain the scrollbars to the right of the corresponding viewport.

Note that left-handed scrollbars are occasionally used elsewhere, as in the X11 Athena Widgets (Xaw) set:

<https://en.wikipedia.org/wiki/X_Athena_Widgets>


For a better reading experience, try the pdf: https://journalofillusion.net/index.php/joi/article/view/983...


I actually liked that they're always visible and not occluded by my thumb on mobile.


Accessibility would be too accessible. For extra fun, make the scrolls bars reversed and inverted axises. After all, it's not like there are disabled people who use assistive devices need simpler, properly-designed websites. Also, it's not GDPR compliant and demands acceptance of cookies.


On mobile, not only did I not get to see the images, I couldn't even leave the site by pressing back. On both chrome and FF on Android.


Yep. Very badly designed / tested UI.

Why can't most websites stick to the basics. Sigh!

I can't imagine what is so unique in presenting this article or this site's content that it requires so much of custom non-standard trickery.


At least for FF on Android, long press the back button to bring up a history list.


That is awesome. I can't wait to see the STL files people make so we can all print them up!

Meanwhile, here is a single mirror illusion STL file and a video showing off how similar illusions work https://www.thingiverse.com/thing:1970522 You can play with the STL in 3D and get a bit of an idea of how it works.


I think you misunderstood this. This is not an illusion of objects from different angles, but an unintuitive transformation of geometry.


They didn’t misunderstand. If you look at the images included in the paper (this link has them inline: https://journalofillusion.net/index.php/joi/article/view/983...) you can see that it is an illusion that can be created with 3D printed objects.


The linked STL is a different Kokichi Sugihara illusion - by the same creator as this new class of illusions, and part of a body of work in this field that this appears to be a continuation of.

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


But it is. Those are objects that are mirror symmetric, and the apparent direction they're facing depends on viewing angle, creating the illusion that they haven't actually been mirrored.


I've implemented some of Sugihara's work earlier. Downloadable files for 3d printing and examples I've shared here: https://github.com/Matsemann/impossible-objects


"Typesetting" loading prompt, and yet they break pgup/pgdn.


The apparent failure to mirror "correctly" left and right in this illusion reminds me of a great interview question I heard: why does a mirror reverse things left and right, but not flip them top and bottom?

It can be fun to watch people scratch their head over it.


The interviewer took it from Feynman:

https://www.youtube.com/watch?v=6tuxLY94LXw


I'm afraid Feynman's already spoiled the answer for me.

N zveebe qbrfa'g syvc yrsg gb evtug, vg npghnyyl syvcf sebag (pybfrfg gb zveebe) gb onpx.


Easy enough for anyone with eyes to see the obvious explanation.


Are you implying _two_ eyes? Because if you think that's the reason, just try closing one eye and looking into a mirror and you'll see that nothing's changed.

(Also, as an exception to your statement, I have eyes, and I wasn't able to grasp why it happens until I watched a video about it.)


This seems like a version of the ambiguous cylinder illusion https://youtu.be/yupxceBjDa0


This feels like a J-class SCP


When so many of the comments begin “for anyone confused” it’s a good sign that you need to go back and redesign your web page…


I am illusioned right now.

Are these special objects? Which figures in the article are thoe being displayed in?

To me, each example basically "works" if you pretend its not a mirror corner but just a solid mirror at an angle. I'm guessing this is not the intent though?


I clicked with the illusion to see and illusion. Now this is a double disillusion.



and youtube video of the 'reveal':

https://www.youtube.com/watch?v=n--zawliqvA


Also, if you're on mobile, switch to the "Desktop site" mode of your browser. I wasn't able to see the figures without setting this.


On the top right, click on "Figures". I almost had the same reaction.


I am now illusioned!


me too! thank you all!


The page on mobile makes me think this an allusion.


Alluding to an elated Aleutian elision?




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