# The hopalong attractorMarch 8, 2015 10:21 PM   Subscribe

These orbits are generated iterating this simple algorithm: (x, y) -> (y - sign(x)*sqrt(abs(b*x - c)), a -x )
posted by slater (19 comments total) 32 users marked this as a favorite

my favorite thing today. I love that you can manipulate it.
posted by bobdow at 10:33 PM on March 8, 2015 [2 favorites]

Screensaver, meh. But I clicked on his About link, and on his blog, oh holy moly

When a Comet met Ganymede

and

The Sky LIVE - Venus Tracker
Wow that's almost as good as Stellarium.app

and

Gauss' method to construct a 17-gon with ruler and compass.

and much other math and astronomy stuff.
posted by charlie don't surf at 10:54 PM on March 8, 2015 [4 favorites]

Apparently the graphics card on my phone is not supported.

Off to light the furnace on the desktop.
posted by Samuel Farrow at 11:02 PM on March 8, 2015 [2 favorites]

Just as a side note, if the simpler mapping (x,y)->(y,-x) had been chosen, for any given point (x,y), you'd get the following resulting points:

(x,y)
(y,-x)
(-x,-y)
(-y,x)
(x,y) (back to where we started)

which is a (usually tilted) square. But since the actual map used perturbs that a bit, it doesn't just loop back to exactly where it started after four iterations, and you get more densely-filled-in and complicated shapes.
posted by Jpfed at 12:27 AM on March 9, 2015

I assume the code is minified in the browser, is there somewhere where it was released?
posted by gryftir at 12:55 AM on March 9, 2015

If you look at the source it appears to be all there, with comments. Calling three.js as described in the "About" pane, of course.
posted by XMLicious at 2:20 AM on March 9, 2015

they should have sent a poet
posted by Sebmojo at 3:05 AM on March 9, 2015 [2 favorites]

But I clicked on his About link, and on his blog, oh holy moly

So in case someone else is as easily confused as me, the hopalong visualization is done by Iacopo Sassarini who has a G+ stream here, but the blog link in Charlie's post is to a blog by Jason Major that Sassarini linked to.
posted by effbot at 3:12 AM on March 9, 2015 [1 favorite]

A little bit of reading, if you like.
posted by Wolfdog at 3:40 AM on March 9, 2015

It's a really lovely image, but it would go much better with some music.(SLYT)
posted by jefflowrey at 3:44 AM on March 9, 2015

Woohoo! Mighty trippy. Thanks for the post.
posted by key_of_z at 4:44 AM on March 9, 2015

That looks... familiar. Similar to Pickover Popcorn, maybe? Anyway, really cool demo.
posted by Leon at 6:51 AM on March 9, 2015

So in case someone else is as easily confused as me, the hopalong visualization is done by Iacopo Sassarini who has a G+ stream here, but the blog link in Charlie's post is to a blog by Jason Major that Sassarini linked to.

Sorry, I got those all from Sassarini's G+ blog but I failed to put in the direct link.

Apparently the graphics card on my phone is not supported.

The screensaver thing does run on my antiquated iPhone 5.
posted by charlie don't surf at 7:00 AM on March 9, 2015

...nor my 2014 MacBook.
posted by bonobothegreat at 7:06 AM on March 9, 2015

Until recently, IIRC, WebGL was disabled by default in the browsers that supported it, so maybe that's the issue for at least some people who are having trouble? In Firefox you could go to the config page and flip a setting. (Though since the entire reason for it to be disabled was that it was classified as "experimental" and hence might cause crashes, if this is the problem it probably would be a better idea to upgrade or use another browser.)
posted by XMLicious at 7:14 AM on March 9, 2015

WebGL seems to be on by default in Safari 8 on my clean install of Yosemite. It is under Preferences>Security>Allow WebGL. In earlier versions of Safari, it can be enabled under the Develop menu (once you enable the Develop menu).
posted by charlie don't surf at 7:21 AM on March 9, 2015

Man, there's a kickass video game idea in this....somewhere.
posted by JoeZydeco at 9:52 AM on March 9, 2015 [1 favorite]

It's like flying through x-ray diffraction.
posted by maryr at 11:15 AM on March 9, 2015

This works well as background music.
posted by scruss at 8:13 PM on March 9, 2015

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