aatish

Haha nice! Try that in wire-frame mode and it looks even crazier: https://twitter.com/aatishb/status/727270083601551360

I left that in as allowable behavior, because our goal with this was not necessarily to model a realistic cloth but more to experience interesting and unusual movements and behaviors. So glitch away!

I'd started off this project by using a fancier ray-tracing method of detecting and avoiding collisions with arbitrary shaped objects. Unfortunately it was just too slow for satisfying real-time performance. So finally, I went with doing the collision detection in a case-by-case way for more simple shapes (ball, table, etc.). The poles would be easy to add as an option, I may try to add that in. Thanks for the suggestion!

Yup, that setting is implemented in a somewhat naive way. The way it works is that I iterate through every pair of points on the cloth, check for when they get too close, and if they are, I introduce a spring to push them apart. So effectively this introduces a short-range repulsive force between pieces of the cloth.

Avoiding self intersections results in more realistic cloth behavior like folds and wrinkles. The problem is, iterating through all pairs of points comes at a computational cost, and can really drop the frame-rate, particularly for large cloths. So I decided to keep this setting off by default until I have a smarter way to implement this (e.g. using quadtrees).

Hi, thanks for voting this up! I created this with a few colleagues. Our goal was to make a fabric simulation tool that might inspire creative exploration among artists and engineers. I hope you find it fun to play with, and welcome any feedback and suggestions on how to improve this.

We started from a three.js cloth simulation example and made a bunch of modifications. The cloth is modeled as a grid of point masses (particles) connected by springs. We've got options for horizontal & vertical springs (simulating cross grain, where the cloth threads run parallel to the edges), diagonal springs (simulating bias grain, where the cloth threads run diagonally), and springs that connect particles two units apart (simulating drape / bending stiffness, similar to a starched tablecloth). It's kind of amazing how a simple system of particles and springs can result in such rich cloth-like behavior. Other than the springs (which are modeled as constraints on the distance between particles), the only forces on the particles are wind and gravity. In addition we have constraints that account for collisions and simulate friction-like behavior.

We've submitted a paper that explains the details of how this works which I'll share once it's published, but for now if you're interested in learning more here are a few references, or google 'verlet integration constraints'. Also happy to try to answer your questions.

https://graphics.stanford.edu/~mdfisher/cloth.html http://www.pagines.ma1.upc.edu/~susin/files/AdvancedCharacte... http://kucg.korea.ac.kr/education/2005/CSCE352/paper/provot9... http://luthuli.cs.uiuc.edu/~daf/courses/Games/SimList/Papers...

Built starting from the Three JS cloth simulation example. Our goal is to create a fabric simulator that can serve as a tool for artistic exploration and expression. Would appreciate any feedback.

The issue, I think, is that experiments like that would only tell you so much, because the insects aren't adapted to the high levels of oxygen (which can be kinda toxic, particularly at higher concentrations). So to really understand this you'd need to breed insects in high oxygen over many, many generations, and have them evolve in this new environment. That takes a lot of time and money. Jon's lab has done it with fruit flies, and they do grow bigger over the generations. But as far as I know (which isn't a lot), folks haven't done those kinds of multi-generation experiments in many species.

Yup, we also have another post that's specifically about the idea you describe: http://noticing.co/on-size-and-warmth/

Great question!

We spoke to Jon Harrison about this (the scientist we interviewed who studies insect growth & respiration). He says that the truth of the matter is we don't know the answer, it's still a hypothesis that the way insects breathe keep them small. There are other competing explanations, like that it's insect's exoskeletons that constrain their size, or ecological arguments (fewer predators means they can grow bigger). Also spiders don't use trachea to breathe but are also small.

One piece of evidence favoring the oxygen hypothesis is research that shows that the fossil record on giant insect size correlates with the oxygen levels in the past, all the way up until birds evolved (and wiped out the ecological niche for giant flying insects!)

http://blogs.discovermagazine.com/notrocketscience/2012/06/0...

And I'm told there's some more interesting work along these lines that's yet to be published.. so hopefully we should know more soon.

Lastly, there's all kinds of experimental work on breeding insects in high oxygen environments, but the results so far aren't universal.. some kinds of insects grow bigger, other's don't. The idea being that oxygen can help the insect grow but can also do damage to cells (in a way similar to aging), so you may need a long while to evolve and adapt to higher oxygen levels.

Hi, I'm one of the authors of the piece. Thanks for voting us up here. Hope you like what we're doing, and let us know what you think. If you're looking to read more of our posts, you can follow the blog on twitter @noticingblog (or on RSS). Cheers.

ok, I think I see the problem. I swapped out that cocktail shaker animation with an animated gif of the same. Hopefully it should work smoothly now. Thanks for your help!

Hi there. Sorry about this, I didn't realize it was 'hijacking scrolling'. I tried a possible fix. Could you let me know if you still see the problem? Thanks.

Hi there - I'm a co-author of the post and put the site together. I'm sorry to hear that the scroll is acting up. I'd like to fix that. Can you (or anyone else seeing this issue) tell me if you see the same behavior on the other posts on the blog or just this one? Thanks.

EDIT: I disabled the 'smooth scrolling' option in my wordpress theme settings to try to fix this. Please let me know if that worked or if you're still seeing the issue. Thanks.

No, it doesn't make sense to track the center of mass of the skateboarder here. If you're interested specifically in the forces on skateboard, you want to track the center of mass on the skateboard. If you include the skateboarder in your system and track the new modified center of mass, you will only see the effect of gravity, being the only remaining external force.

The sound was only audible up to 3000 miles in radius, or about 1/13th the globe. It wasn't audible in the other side of the Earth (although it was detectable.)

The Tsar bomb was in the ballpark of a 50 megaton explosion, whereas estimates that I've seen for Krakatoa put it at up to 200 megatons. That said, there would be differences due to the fact that h-bombs are exploded at a height to maximize the damage from the blast wave, and that a significant fraction of Krakatoa's energy would have been spent on throwing earth around. It's always hard to compare different explosions because it's difficult to know what fraction of the energy output goes into acoustic energy, but I think it's reasonable to assume that Krakatoa was louder (at least in that the sound was heard further).

I was also captivated by this vivid first person account of a Dutch pilot in the coastal town of Anjer who survived the ensuing Tsunami http://www.vansandick.com/familie/links/vulcaan2.php#h1

Hey, I'm the author of the post (on twitter @aatishb). Thanks for voting it up. Would love to hear your thoughts and constructive feedback. Cheers. (PS the references linked to at the bottom of the post are packed with fascinating information about Krakatoa, for anyone who wants to dig deeper.)

Thanks for pointing that you. My goal was to point out an empirical observation that can't be explained by a local hidden variables theory. You're right that I didn't explain how quantum mechanics predicts the same result, because that's tricky to do in the scope of such an article.

Here's a little more on that: One way you could do this experiment is to create 2 entangled electrons. Measuring the spin of an electron in the x, y,or z direction corresponds to the 3 doors on the box. Spin in a given direction is a binary variable for an electron (up or down) so that corresponds to the color of the light in each door (red or green).

Since the electrons are entangled, if you measure the spin of one of them in the x direction (say), then this also constitutes a measurement of the spin of the other particle in the x direction. And you can show using quantum mechanics that if you measure the spin of an electron in the x direction, the spin in the y or the z direction will be up with probability 50% and down with probability 50%. I left this as an empirical fact because I don't know how to explain it with actually resorting to doing quantum mechanics.

Sweet. Hi! This is an odd place to bump into you. :)

I agree with your thoughts that this could be a consequence of coating the top surface in the waxy needles. However, I think it's actually somewhat unusual for a leaf to be superhydrophobic on the top and bottom, so I was wondering if there was some specific advantage to this leaf. Also, the needles on the under-side seemed far more dense than those on top, which was interesting.

Yeah, I linked to Neverwet in the post. The video demos are amazing although in practice I hear that the coating fades pretty quickly. But it's cool to see commercial applications of superhydrophobic surfaces.

Have been meaning to read that, and just borrowed it from the library on your suggestion. Thanks!

Thanks!

Hi. The needles are wax structures that protrude from the leaf, they aren't part of the leaf. So the added surface area doesn't absorb any air, and I doubt it helps in evaporative cooling either.

Hey, I know an A. Manfredi. Are you Anthony from Swat?

Hey - I'm the author of this piece. Thanks for voting it up to the front page. I love finding cool science in ordinary/everyday places, and am curious to hear people's responses to the piece. Cheers.

Hi. Author of the piece here. Thought this might be of interest to the Hacker News audience. I'm interested in hearing people's feedback and reactions to the piece.

In the article I described the discrete fourier transform, but there is a continuous version, where a signal is represented by an infinite sum (really an integral) of component frequencies. This is the version that is more generally useful. Here's a great animation by LucasVB of the continuous fourier transform in action: http://upload.wikimedia.org/wikipedia/commons/a/a3/Continuou...

This is actually really valuable feedback and one of the things I like about the HN audience. I struggle to strike a balance between precision and simplicity, and your comments raised many interesting subtleties that I had overlooked. So thanks for helping me get a better handle on this.

Thanks for your feedback. Sure, any digital signal is by definition finite in its resolution (the sample rate or bits). I was trying to address the distinction between wave files of the type stored on audio CDs, and MP3s - both digital signals. I agree that the Fourier transform is in principle lossless, but it's particularly useful to use it in a lossy way, i.e. to throw out the least important (to us) components of the signal. If I was particularly misleading about this, I'd like to know.

Hi Hacker News - I'm the author of the piece, also on twitter @aatishb. Look forward to hearing your thoughts. I encourage you to share your thoughts and insights with other readers by leaving a comment on the post, particularly if you know of other interesting applications about the Fourier transform. Cheers!