Ultrathin business card runs a fluid simulation • Hacker News Board

Re: Ultrathin business card runs a fluid simulation

#231

Post by fennecfoxy » Mon, Aug 11, 2025, 10:35 AM UTC

DonHopkins wrote: post #133

fennecfoxy wrote: post #52

Earlier quoted context omitted.

Stuff like that is dead now btw (yes, it makes me sad too). Kids have iPhones; the idea is great but can just be an app. Which tbf makes more sense because you get the benefit of imu & everything else for that behaviour. Remember those little LCD cube block toys with the stick dudes that lived in 'em, then when you plug 'em together they interact? Those were the days.

The Movable Feast Machine (movablefeastmachine.org) 44 points by mekaj on Nov 20, 2015 | hide | past | favorite | 11 comments https://news.ycombinator.com/item?id=10600001 The T2 Tile Project: https://www.youtube.com/channel/UC1M91QuLZfCzHjBMEKvIc-A Artificial Life Creation T-0 and Launching - T2sday Update 3135: https://www.youtube.com/watch?v=O8kOkLPwNNw

Cool thanks for the links but are they mass produced commercial products known & bought worldwide? Because that's what I was referring to; kinda the digital but pre-touchscreen-slab type devices age of 80s-2010s.

Re: Ultrathin business card runs a fluid simulation

#232

Post by N2yhWNXQN3k9 » Mon, Aug 18, 2025, 7:45 AM UTC

kazinator wrote: post #209

N2yhWNXQN3k9 wrote: post #193

Earlier quoted context omitted.

increase viscosity of said fluid

It doesn't work that way, unfortunately. The virtual fluid represented by the LEDs does not move anything like syrup. It's like looking at a small image of water sloshing in a big tank. To get of fluid to behave that way on the scale of several inches, the fluid would have to be massive (very dense) while simultaneously gravity would have to be reduced.

Viscosity is literally a function of how a fluid behaves, but okay, whatever, probably a good take

Defined as:

> a change in shape or to movement of its neighboring portions relative to one another

Re: Ultrathin business card runs a fluid simulation

#233

Post by dragonwriter » Mon, Aug 18, 2025, 8:00 AM UTC

kazinator wrote: post #209

N2yhWNXQN3k9 wrote: post #193

Earlier quoted context omitted.

increase viscosity of said fluid

It doesn't work that way, unfortunately. The virtual fluid represented by the LEDs does not move anything like syrup. It's like looking at a small image of water sloshing in a big tank. To get of fluid to behave that way on the scale of several inches, the fluid would have to be massive (very dense) while simultaneously gravity would have to be reduced.

> It doesn't work that way, unfortunately

It works exactly that way.

> To get of fluid to behave that way on the scale of several inches, the fluid would have to be massive (very dense) while simultaneously gravity would have to be reduced.

No, it would just need to be very viscous. Viscosity is literally resistance to flowing, density is not, and a less dense fluid can nevertheless also be more viscous (honey is less dense than saltwater, but saltwater is much less viscous at STP [standard temperature and pressure, 0°C and 1atm], while mercury is significantly more dense than granite but something like 23 orders of magnitude less viscous at STP.)

Re: Ultrathin business card runs a fluid simulation

#234

Post by kenny239 » Wed, Aug 20, 2025, 9:37 AM UTC

delichon wrote: post #170

Advantages of a business card sized hollow box partially filled with water: * more realistic fluid motion * cheaper, easier build * easier to debug Disadvantages: * risk of wet butt when you sit down * less joy of doing hard things

things you get away with when you remove one level of simulation...