5 ms·

Sugihara's Dog

258 points by sohkamyung 4y ago

avpix 4y ago
This is a fantastic demonstration of a pseudovector! https://en.wikipedia.org/wiki/Pseudovector https://en.wikipedia.org/wiki/Pseudovector
- deleted 4y ago
  [deleted]
js2 4y ago
If you, like me, are one of today's lucky ten thousand[1], here's some context: Kokichi Suhihara is an engineering professor who designs 3D objects that create optical illusions, including their mirrored images. Here's his English home page: http://www.isc.meiji.ac.jp/~kokichis/Welcomee.html http://www.isc.meiji.ac.jp/~kokichis/Welcomee.html So we're looking at a photo of an actual 3D object and its mirrored reflection, which should obviously appear incorrect since, well, the reflection is not apparently mirrored but rather facing the same way as the real object. I think the key to understanding what we're seeing is that the non-mirrored image is also not as it appears. We'd need to see it rotated to understand the actual shape. Here's a short YouTube video of his "Ambiguous Garage Roof" that I've now watched several times and it keeps blowing my mind: https://youtu.be/KtA6u1HIqbg https://youtu.be/KtA6u1HIqbg [1] https://xkcd.com/1053/ https://xkcd.com/1053/
- the_af 4y ago
  > Here's a short YouTube video of his "Ambiguous Garage Roof" that I've now watched several times and it keeps blowing my mind: > https://youtu.be/KtA6u1HIqbg https://youtu.be/KtA6u1HIqbg What the... What's amazing about the Ambiguous Garage is that even after I've seen how the illusion is done, my brain keeps getting fooled. It's one of those things where it's simply impossible not to "see" the illusion even after you understand it.
  - js2 4y ago
    It reminds me of the Penn and Teller red ball routine where they tell you how it works before they perform it and your brain (well, mine anyway) still won't accept it. https://youtu.be/W2T-YUd_Om4 https://youtu.be/W2T-YUd_Om4 https://www.thisamericanlife.org/extras/the-floating-ball-routine-an-excerpt-from-david-p-abbotts-book-of-mysteries https://www.thisamericanlife.org/extras/the-floating-ball-ro...
- omershapira 4y ago
  Funny story: In 1984, my mom, a Computational Geometry researcher, saw a proof [1] in some IEEE journal that she was annoyed with. It seemed way too general and was too easy to disprove, so she did [2], in a subsequent publication, with the author's name in the title. She later told me he courteously publicized a correction, credited her, and would mail her pre-prints for his papers since. Earlier this year I looked up the claim and counterclaim: Turns out it's Kokichi Sugihara. I guess in the 80s well-actuallying in Mathematics journals was good form. :) [1] https://ieeexplore.ieee.org/document/4767571 https://ieeexplore.ieee.org/document/4767571 [2] https://ieeexplore.ieee.org/document/4767487 https://ieeexplore.ieee.org/document/4767487
hammock 4y ago
Is there a place to buy these? Or download the plans and somewhere that will print them for you?
- CobrastanJorji 4y ago
  Here's a star/heart that's the same idea: https://www.myminifactory.com/object/3d-print-ambiguous-star-to-heart-illusion-210605 https://www.myminifactory.com/object/3d-print-ambiguous-star... I've printed it and physically fiddling with it made it much more clear how it worked. I haven't seen a print for that dog, though. In theory, I think you could use Sugihara's approach to automatically generate such a model for most closed curves. That'd be a cool little program that I don't know how to write.
IIAOPSW 4y ago
Remember folks, if you're unsure, illusions don't have shadows.
- turtleyacht 4y ago
  That.. sounds like you have a bag of old-school RPG tricks? I wish you did. Thanks for this one.
  - IIAOPSW 4y ago
    Thanks. I meant it literally and figuratively. Literally, drawing shadows of optical illusions generally makes them stop being optical illusions. Figuratively, all illusory experiences (magic tricks, scams, psychotic delusions) tend to have some mundane inconsistency which is likely to go unnoticed, but if you know to look for it the illusion evaporates. Illusions don't have shadows.
pvaldes 4y ago
So the dog structure is a "3D palindrome", it seems.
dark-star 4y ago
His illusions are awesome. Even if you know how they work (watch his videos), your brain will still not be able to completely comprehend them. That's what makes a good optical illusion.
- coldpie 4y ago
  It took me an embarrassingly long time to even realize what the illusion was.
  - DMell 4y ago
    I still don't. Can someone explain?
    - Hamuko 4y ago
      How do objects normally appear when viewed in a mirror?
      - DMell 4y ago
        Okay - wow..
      - 0xbadcafebee 4y ago
        [dead]
      - IIAOPSW 4y ago
        reflected
    - lm28469 4y ago
      The dog appears to be facing the same way, even in the reflection
    - deleted 4y ago
      [deleted]
    - too_damn_fast 4y ago

258 points by sohkamyung 4y ago

This is a fantastic demonstration of a pseudovector! https://en.wikipedia.org/wiki/Pseudovector https://en.wikipedia.org/wiki/Pseudovector

deleted 4y ago
[deleted]

js2 4y ago

If you, like me, are one of today's lucky ten thousand[1], here's some context: Kokichi Suhihara is an engineering professor who designs 3D objects that create optical illusions, including their mirrored images. Here's his English home page: http://www.isc.meiji.ac.jp/~kokichis/Welcomee.html http://www.isc.meiji.ac.jp/~kokichis/Welcomee.html So we're looking at a photo of an actual 3D object and its mirrored reflection, which should obviously appear incorrect since, well, the reflection is not apparently mirrored but rather facing the same way as the real object. I think the key to understanding what we're seeing is that the non-mirrored image is also not as it appears. We'd need to see it rotated to understand the actual shape. Here's a short YouTube video of his "Ambiguous Garage Roof" that I've now watched several times and it keeps blowing my mind: https://youtu.be/KtA6u1HIqbg https://youtu.be/KtA6u1HIqbg [1] https://xkcd.com/1053/ https://xkcd.com/1053/

the_af 4y ago
> Here's a short YouTube video of his "Ambiguous Garage Roof" that I've now watched several times and it keeps blowing my mind: > https://youtu.be/KtA6u1HIqbg https://youtu.be/KtA6u1HIqbg What the... What's amazing about the Ambiguous Garage is that even after I've seen how the illusion is done, my brain keeps getting fooled. It's one of those things where it's simply impossible not to "see" the illusion even after you understand it.
- js2 4y ago
  It reminds me of the Penn and Teller red ball routine where they tell you how it works before they perform it and your brain (well, mine anyway) still won't accept it. https://youtu.be/W2T-YUd_Om4 https://youtu.be/W2T-YUd_Om4 https://www.thisamericanlife.org/extras/the-floating-ball-routine-an-excerpt-from-david-p-abbotts-book-of-mysteries https://www.thisamericanlife.org/extras/the-floating-ball-ro...
omershapira 4y ago
Funny story: In 1984, my mom, a Computational Geometry researcher, saw a proof [1] in some IEEE journal that she was annoyed with. It seemed way too general and was too easy to disprove, so she did [2], in a subsequent publication, with the author's name in the title. She later told me he courteously publicized a correction, credited her, and would mail her pre-prints for his papers since. Earlier this year I looked up the claim and counterclaim: Turns out it's Kokichi Sugihara. I guess in the 80s well-actuallying in Mathematics journals was good form. :) [1] https://ieeexplore.ieee.org/document/4767571 https://ieeexplore.ieee.org/document/4767571 [2] https://ieeexplore.ieee.org/document/4767487 https://ieeexplore.ieee.org/document/4767487

hammock 4y ago

Is there a place to buy these? Or download the plans and somewhere that will print them for you?

CobrastanJorji 4y ago
Here's a star/heart that's the same idea: https://www.myminifactory.com/object/3d-print-ambiguous-star-to-heart-illusion-210605 https://www.myminifactory.com/object/3d-print-ambiguous-star... I've printed it and physically fiddling with it made it much more clear how it worked. I haven't seen a print for that dog, though. In theory, I think you could use Sugihara's approach to automatically generate such a model for most closed curves. That'd be a cool little program that I don't know how to write.

IIAOPSW 4y ago

Remember folks, if you're unsure, illusions don't have shadows.

turtleyacht 4y ago
That.. sounds like you have a bag of old-school RPG tricks? I wish you did. Thanks for this one.
- IIAOPSW 4y ago
  Thanks. I meant it literally and figuratively. Literally, drawing shadows of optical illusions generally makes them stop being optical illusions. Figuratively, all illusory experiences (magic tricks, scams, psychotic delusions) tend to have some mundane inconsistency which is likely to go unnoticed, but if you know to look for it the illusion evaporates. Illusions don't have shadows.

pvaldes 4y ago

So the dog structure is a "3D palindrome", it seems.

dark-star 4y ago

His illusions are awesome. Even if you know how they work (watch his videos), your brain will still not be able to completely comprehend them. That's what makes a good optical illusion.

coldpie 4y ago
It took me an embarrassingly long time to even realize what the illusion was.
- DMell 4y ago
  I still don't. Can someone explain?
  - Hamuko 4y ago
    How do objects normally appear when viewed in a mirror?
    - DMell 4y ago
      Okay - wow..
    - 0xbadcafebee 4y ago
      [dead]
    - IIAOPSW 4y ago
      reflected
  - lm28469 4y ago
    The dog appears to be facing the same way, even in the reflection
  - deleted 4y ago
    [deleted]
  - too_damn_fast 4y ago