aplavin

7 ms·

1.
by aplavin 1mo ago
> I do wonder if you do like, size estimates of a black hole in my room. Suppose I have a black hole in my room, I'd be curious to know what the mass of that is, like a fun fact, tidbit somewhere. Forgot to answer this first! Basica
2.
by aplavin 1mo ago
Would MSAA compute more samples, effectively multiplying shader computation? Ideally, it should be something adaptive, to the number of pixels/device compute power, eg compute 2x smaller resolution on phones/retina, compute 1x res
3.
by aplavin 2mo ago
> I thought "oooh this is interesting I wonder how they are going to do physically accurate on an end device" Recalling how the original particle sim was something like 100TB, took 2 weeks to generate and seemed to write in a w
4.
by aplavin 2mo ago
Hmmm I think I see what's happening here. Basically, all devices I tested (laptops/phones/tablets) seem to have small pixel size, and to save on compute power for weaker devices I decided to render with half as many pixels as
5.
by aplavin 2mo ago
The vast majority of scientific images, be it in papers on press releases, are using an arbitrarily-chosen colormap to map whatever numeric values are there to actual visible pixels. For the Event Horizon Telescope speficially – it is a rad
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by aplavin 2mo ago
To describe cow's gravity? Pretty much so. Then, for visualization and even for many biological purposes, it's accurate enough to mode the cow as a bunch of organs with known processes happening in them. But that's still far
7.
by aplavin 2mo ago
>> I follow the by-far-dominant approach in scientific literature, where color mapping choice is completely unrelated to physical accuracy of the plotted observations or simulations. > It is not true at all that this is the dominan
8.
by aplavin 2mo ago
> why the stars surrounding the black hole are just points, and more over why the lines are straight to the centre of the hole Sorry for confusion! Points + lines are just other users looking at the black hole right now, their camera loc
9.
by aplavin 2mo ago
That would be fun indeed! Not sure I would literally want to put this into my room though.
10.
by aplavin 2mo ago
You mean, without a camera and a screen, out of pure physical objects? You can actually reproduce gravitational light bending quite accurately with a properly-shaped lens (some wine glasses are surprisingly close!), see eg https:/&#x2
11.
by aplavin 2mo ago
Could you please share a screenshot so that I investigate what actually happens? I tested on a few different devices, but far from anything extensive.
12.
by aplavin 2mo ago
Hmm, interesting! I saw that it's a draft, and didn't investigate further. Maybe it does work indeed on some browsers. Generally, the compatibility story turned out more fragmented than I expected. Eg, on my phone, Chrome can do A
13.
by aplavin 2mo ago
> not using a perceptually uniform colormap in the year 2026 is quite a blunder Then you are up for a big surprise if you browse through modern published papers :)
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by aplavin 2mo ago
> What exactly is physically accurate here though? I'll assume this is a good faith question, hope it was intended like one. I view strong light bending as the key distinguishing property of a black hole, and something we are fairly
15.
by aplavin 2mo ago
Note that most of the points you raised are clearly not bugs – most notably, things like non-rotating black hole or colormap choice. At the very most, these can be considered missing features, but they don't affect correctness in any w
16.
by aplavin 2mo ago
Arguing about colormap choice seems very strange to be – this is such a common practice in astronomy (and other fields!). The vast majority of images you see in published papers apply some arbitrarily-chosen colormap and color scheme. No ma
17.
by aplavin 2mo ago
That option for rotating (Kerr) black holes generally works, but not on all devices in my experiences. Debugging on someone's phone is not that straightword, so I went with the most accessible experience by default. Also note that the
18.
by aplavin 2mo ago
> AR + camera warping don't work together, unfortunately – browser API limitations. So, you either choose AR and see the simulated emission from around the black hole, properly warped/boosted – but the camera feed remains flat,
19.
by aplavin 2mo ago
Yes, even observing a single jet pointed towards us (typically, at just a few degrees) is routinely used a strong argument for existence of many similar powerful sources, just misaligned with the Earth. Arguments like: - See a jet at redshi
20.
by aplavin 2mo ago
It's purely my color map choice – the underlying simulated image is simply a number at each pixel. Transforming that number to the actual displayed color is generally an arbitrary choice, as common for the vast majority of images in as
21.
by aplavin 2mo ago
Sure, see https://blackhole.plav.in/ar_example.mp4 for an example. Should work on most Android phones, even old ones (mine is 7 years), the Chrome browser is generally best for AR. Interestingly, Firefox seems to be better
22.
by aplavin 2mo ago
Sure, most of the raised questions are reasonable potential feature additions to be made – things like rotating black holes, or linear brightness-to-screen-pixel mapping. They just aren't "inaccuracies", in my opinion.
23.
by aplavin 2mo ago
Eagerly awaiting WebGravity API support to control your device's builtin gravity field generator!
24.
by aplavin 2mo ago
Yes, as said in the text, unfortunately this is a limitation of browser APIs. You either get AR and no access to the camera feed (this is the AR mode here, black hole floating in your room, simply overlaid on top of the camera feed) or get
25.
by aplavin 2mo ago
Colormap/colorscale is generally considered an arbitrary choice in scientific plots or visualizations. Linear mapping of simulated emission brightness -> screen brightness could be a reasonable alternative mode, I agree – but it&#x2
26.
by aplavin 2mo ago
Yes, linked in the readme! They simulate light bending, but ignore time delay effects. I think the earliest of these black-hole-camera renderings is https://dominic-chang.com/bhi-filter/ though (also linked in readme)
27.
by aplavin 2mo ago
> Its titled a "physically accurate black hole"! Please don't do this, if its intentionally not physically accurate and heavily simplified! It also doesn't exert the gravity an actually accurate black hole should :) A
28.
by aplavin 2mo ago
Now I think I see what you meant. There actually are no upper/lower limits on the black hole size (in classical physics – ignoring quantum effects). Compressing the Earth to ~1 cm in size would give you a black hole, and its event hori
29.
by aplavin 2mo ago
Actually, the jet was the first part of the app – I wanted to just see and "feel" relativistic beaming in practice, in physical space. And it was fun and instructive indeed! Really puts into perspective how tight is the jet vs lin
30.
by aplavin 2mo ago
Some are fair – of course this is a simplified visualization! Observationally, we don't really know how fast a given black hole is rotating, and here I indeed assumed a non-rotating one. It's not an inaccuracy per se, more like a

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