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rhn_mk1 commented on Simulating fluids, fire, and smoke in real-time   andrewkchan.dev/posts/fir... · Posted by u/ibobev
jameshart · 2 years ago
My favorite example of the lie-concealed-within-the-lie is the ‘Half-Life Alyx Bottles’ thing.

Like, watch this video: https://www.youtube.com/watch?v=9XWxsJKpYYI

This is a whole story about how the liquids in the bottles ‘isn’t really there’ and how it’s not a ‘real physics simulation’ - all just completely ignoring that none of this is real.

There is a sense in which the bottles in half-life Alyx are ‘fake’ - that they sort of have a magic painting on the outside of them that makes them look like they’re full of liquid and that they’re transparent. But there’s also a sense in which the bottles are real and the world outside them is fake. And another sense in which it’s all just tricks to decide what pixels should be what color 90 times a second.

rhn_mk1 · 2 years ago
I want to see that shader. How is sloshing implemented? Is the volume of the bottle computed on every frame?

Clearly, there's some sort of a physics simulation going on there, preserving the volume, some momentum, and taking gravity into account. That the result is being rendered over the shader pipeline rather than the triangle one doesn't make it any more or less "real" than the rest of the game. It's a lie only if the entire game is a lie.

rhn_mk1 commented on What This Country Needs is an 18¢ Piece (2002) [pdf]   cs.uwaterloo.ca/~shallit/... · Posted by u/cokernel_hacker
WalterBright · 2 years ago
I've noticed that dollar bills are cheaper than wallpaper. Wouldn't it be fun to do a room in dollar bills! My very own Scrooge McDuck cash vault!

But there's probably some killjoy law that makes this illegal.

rhn_mk1 · 2 years ago
https://www.wayfair.com/decor-pillows/sb1/roll-wallpaper-c18...

> Britiany Peel & Stick Floral Roll by Canora Grey

> From$1.20/sq. ft.

https://www.ehd.org/science_technology_largenumbers.php

> The area covered by 100 one dollar bills measures 11.13 square feet.

comes out to about $9/sq. ft., about 9 times as expensive.

But 1USD=90RUB today, and the lowest denominated note is 5RUB, coming out to 1USD=18notes. Each note is 137 mm × 61 mm, coming out to about 0.09 sq. ft. (if I'm not mistaken). Then 1USD=1.62 RUB sq. ft., so it costs

$0.62/sq. ft.

to have a green wall of ~~current~~ obsolete Russian currency.

What's surprising is that you can afford it even if you live in Russia. According to Obi and this roll of wallpaper:

https://oboi-store.ru/catalog/bumazhnye

> JB80201 Обои KT Exclusive Jelly Beans

> 10.05х0.53м

> 10 500 руб/рул.

the price per area isn't that different, coming out to about $2/sq. ft., meaning that if you have a clever way to paste all the single notes easily and know how not to get in any potential trouble with the law, it makes economical sense to get your wallpaper at the bank.

EDIT: according to Wikipedia, the note has been replaced by coins, and the next one is almost but not quite 10x as expensive by area.

rhn_mk1 commented on What is the index of an empty string in an empty string?   successfulsoftware.net/20... · Posted by u/hermitcrab
cyrusmg · 2 years ago
What's the logic behind returning anything but -1 (not found) ?

Given "asdf".indexOf("a") is 0

Then "asdf"[0] is "a"

--

Given "".indexOf("") is 0

Then ""[0] is "" (which it's not in any language I know of)

rhn_mk1 · 2 years ago
"asdf".indexOf("as") is 0

but

"asdf"[0] is NOT "as".

so there can be no expectation that ""[0] is "".

Those two operations are not related to each other. It's more intuitive if you treat .indexOf() as .startOf(). Then "asdf"[0..x] is "as" for x=2, and ""[0..x] is "" for x=0.

rhn_mk1 commented on Do black holes have singularities?   arxiv.org/abs/2312.00841... · Posted by u/wrycoder
nicbn · 2 years ago
But to know via scientific method requires proof (or disproof) by experimentation
rhn_mk1 · 2 years ago
You can get knowledge (e.g. mathematical) without observation. You can't get information without observation.
rhn_mk1 commented on Do black holes have singularities?   arxiv.org/abs/2312.00841... · Posted by u/wrycoder
lmm · 2 years ago
> Is prediction differs from information about future?

Yes, prediction doesn't and can't contain information (in the technical sense) from the future, since by definition it's based only on what we know in the present.

> Do we have some ideas why rules of physics will be different in the future?

No. It's perfectly reasonable to assume that the rules of physics will be the same in the future. Just as it's perfectly reasonable to assume that they're the same inside a black hole. But in both cases we can't know.

rhn_mk1 · 2 years ago
"Reasonable" is an unfortunate word IMO. An assumption doesn't come out of reasoning. We can't even estimate the probability of this assumption being right because we can't see the future.

The best way this word fits is that we can reason towards the conclusion that whether laws will change or not is an assumption.

rhn_mk1 commented on Ask HN: What apps have you created for your own use?    · Posted by u/fuzztester
rhn_mk1 · 2 years ago
A script to arrange 2 pages of a PDF side-by-side.

Another bunch takes care of creating invoices, gathering bank statements, and paying using the bank account.

Finally, a temperature limiting daemon because thermald doesn't seem to work.

rhn_mk1 commented on MemoryCache: Augmenting local AI with browser data   future.mozilla.org/blog/i... · Posted by u/NdMAND
linsomniac · 2 years ago
I would sure love a way to "chat" with my browsing history and page content. Is there any way to automatically save off pages that I've visited for later processing? I looked a decade or more ago and didn't really find a good solution.
rhn_mk1 · 2 years ago
rhn_mk1 commented on How to run 50% faster without external energy (2020)   science.org/doi/10.1126/s... · Posted by u/beefman
tourist2d · 2 years ago
> to keep the foot from sliding

So you obviously have never used clip in bike pedals before. Why are you trying to argue this point if you know nothing about what you're talking about?

rhn_mk1 · 2 years ago
If you're clipped in, why would you keep feet from sliding?

Preventing sliding by pushing is how effort is wasted and is a possible explanation why a cyclist might feel much stronger when clipped in and no longer has to push - while attributing the lower effort to the upstroke pull.

rhn_mk1 commented on How to run 50% faster without external energy (2020)   science.org/doi/10.1126/s... · Posted by u/beefman
stouset · 2 years ago
> The idea that your muscles have enough strength on the upstroke to contribute meaningfully to cycling is actually a bit of a misunderstanding.

Absolutely not, and there are plenty of easy counterexamples.

If you've ever raced track, team pursuits start from a dead standstill. You have to expend a ton of force to turn a huge gear, and the contribution of the lifting leg is crucial to getting up to speed. Of course it's not going to contribute as much as your lead leg, but all four of your limbs are at maximum exertion getting the bike up to speed. Even not racing at a track, you can test this on any road bike. Shift into high gear, come to a standstill, and time yourself getting up to speed.

Another trivial counterexample that anyone (with clipless pedals) can test is a hill climb. Being able to lift on the upstroke is an enormous additional benefit and the difference can be easily measured and proven. Perform a lengthy climb with and without involving your trailing leg, at a given level of intensity. Repeat this multiple times, and it will be patently obvious that your trailing leg is performing significant useful work. The steeper the climb, the more important this is.

Sprint finishes are another place where this is critically important, but it's harder to set up a simple test.

What all of these have in common are situations where outputting a higher force is more important than long-term endurance. Lifting on the upstroke is difficult to do at high pedal speeds, but at medium or low pedal speeds, it's a clear differentiator.

rhn_mk1 · 2 years ago
Those are not necessarily examples of lifting. Those could as well be explained by the contribution of not pressing on the opposite pedal (to keep the foot from sliding).

And not pressing doesn't shine any light on the force of lifting.

rhn_mk1 commented on Beginners guide to building a hardware hacking lab   voidstarsec.com/hw-hackin... · Posted by u/wrongbaud
JohnFen · 2 years ago
That doesn't explain it, though. You don't need a microcontroller for that. I suspect the real answer is "to minimize parts count".
rhn_mk1 · 2 years ago
Is there a fixed-function circuit that can read a digital value out of a sensor and compare it with a threshold?

I'm not dounting it's possibly, but I'd be surprised if it's available without involving a Turing-complete computer.

u/rhn_mk1

KarmaCake day3392August 1, 2017
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Trying to be nicer.

https://github.com/rhn/ https://gitlab.com/rhn/

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