"right facing arrow"

Started by ortwin, March 19, 2023, 03:07:55 PM

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ortwin




Just yesterday I found out about the existence of this striking optical illusion.
Many many pictures and videos of this are on the internet - how to make it and all.
The following video is from the Kokichi Sugihara who came up with this, enjoy. A lot more great illusions can be found on his YouTube channel.


https://www.youtube.com/watch?v=vGxTKpOt6xU&t=1s








In the broader world of tops, nothing's everything!  —  Jeremy McCreary

ta0

I hadn't seen that video but I have 3D-printed the circle-to-square illusion invented by the professor. Even looking with two eyes the illusion is strong.

I think I'm going to design and print one with the profile of a spinning top . . .

ortwin

I came across this in the twisty puzzle forum where somebody printed a 2x2x2 cube with the arrow illusion.



In the broader world of tops, nothing's everything!  —  Jeremy McCreary

ta0

Here is my version of a right-pointing spinning top (profile):



I also designed, but haven't printed, a forward pointing top (when you rotate it 180 degrees it still points towards you).

ortwin

Nice!
Whats the maximum spin time?
Show us how you do a boomerang with it!
Can you do regeneration tricks with this top?


In the broader world of tops, nothing's everything!  —  Jeremy McCreary

ta0

Quote from: ortwin on March 23, 2023, 02:11:48 AM
Nice!
Whats the maximum spin time?
Show us how you do a boomerang with it!
Can you do regeneration tricks with this top?

My record is 7 or 8 seconds spinning it with the fingers, but not around the apparent tip:



This is actually a principal axis because of its symmetry, so it's stable.

Until you asked, I would have said it was impossible to boomerang. Now I'm thinking that it may be possible to wrap a string around it . . . It would be a major challenge, though.

Given the profile and symmetry, it's impossible to regenerate by blowing air directly from above. But it seems to me that blowing air at 45 degrees could in theory regenerate.

ortwin

#6
Due to the color it reminds me a bit of that Rubik's lemon we made tops of (link).


The picture you first posted of that profile is really impressive, but how would you rate it when viewed directly?
With two eyes, not exactly from the angle it was designed for?
Still worth making it?

In the broader world of tops, nothing's everything!  —  Jeremy McCreary

ta0

#7
Quote from: ortwin on March 23, 2023, 02:41:07 PM
The picture you first posted of that profile is really impressive, but how would you rate it when viewed directly?
With two eyes, not exactly from the angle it was designed for?
Still worth making it?

I think with both eyes it's still impressive. I designed it for 45 degrees viewing, but probably from 30 to 60 degrees it's still pretty good. If you move to the right, the illusion breaks, but less so if you move to the left.
You would be able to see that the surface is wavy (specially if the lighting is not diffuse). But even when you grab it and you feel the shape and you turn it slowly 180 degrees, it's still somewhat eerie to see the crown become the tip and vice versa.
Perhaps by painting it so it darkens towards the edges, the illusion that it has the correct 3D shape of a top could be enhanced.

If you want to print it, I can upload the stl file to Thingiverse. Or I can give you one when we finally meet.
It's not difficult to design your own illusion of this type using CAD software. You extrude two cylinders at opposite angles with the base profiles that you want and intersect them.

I just realized that you can get a spooky effect: if you illuminate it straight, you get a shadow that corresponds to the profile but on the mirror image the profile flips while the shadow remains the same.  :o