Can you post a demo video of the AR/VR with the effects?
Apparently it is not working correctly on my device, so it would be nice to see the intended effect.
Show HN: Physically accurate black hole you can put in your room
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Re: Show HN: Physically accurate black hole you can put in your room
#142Earlier quoted context omitted.
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> and they didn't know any better. i think an " astrophysicist at Harvard's Black Hole Initiative studying quasars and black hole environments " who " work[s] with raytracing/radiative transfer simulations professionally "probably has a decent understanding of what's going on...
You'd think, and yet, they happily slapped the Harvard BHI name on something that doesn't do what it says on the tin. I think ignorance is preferable to deliberate deception, so I assumed ignorance.
Re: Show HN: Physically accurate black hole you can put in your room
#143Earlier quoted context omitted.
> and they didn't know any better. i think an " astrophysicist at Harvard's Black Hole Initiative studying quasars and black hole environments " who " work[s] with raytracing/radiative transfer simulations professionally "probably has a decent understanding of what's going on...
You'd think, and yet, they happily slapped the Harvard BHI name on something that doesn't do what it says on the tin. I think ignorance is preferable to deliberate deception, so I assumed ignorance.
i think they've made some decently reasonable comments explaining their choices, whether you agree or not, and coming in with a shallow dismissal solely consisting of "llm garbage, must be an idiot" is a pretty shitty thing to do (let alone specifically against the rules).
20k's comments open up conversation and engage with the content. yours is just boring, encourages no conversation, and is basically a copy/paste of thousands of other worthless comments. the only thing your comment accomplishes is making hn a worse place.
Re: Show HN: Physically accurate black hole you can put in your room
#144Can you post a demo video of the AR/VR with the effects? Apparently it is not working correctly on my device, so it would be nice to see the intended effect.
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 for the camera mode – for me, Chrome only gives one camera feed at a time, while Firefox allows both front & rear cameras.
And AR + camera warping don't work together, unfortunately – browser API limitations.
Re: Show HN: Physically accurate black hole you can put in your room
#145Can you post a demo video of the AR/VR with the effects? Apparently it is not working correctly on my device, so it would be nice to see the intended effect.
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 for the camera mode – for me, Chrome only gives one camera feed at a time, while Firefox allows both front & rear cameras. And AR + camera warping don't work together, unfortunately – browser API l…
Okay either I'm stupid or not seeing the "relativistic effects".
This looks the same as on my device.
I was expecting some distortion or bending of the background?
Re: Show HN: Physically accurate black hole you can put in your room
#146If anyone's interested in the accuracy, this is very 'visualisation grade' software. Its a bit of a pet peeve of mine that people present these sims as being very physically accurate, when they contain major inaccuracies, some of which are very obvious and/or deliberate. This one has some serious physical limitations I wouldn't mind at all if it didn't say that this was a *physically accurate* black hole specifically…
at 1 - is it red due to red shifting due to gravity?
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 astronomy/astrophysics papers. The only difference is that I don't show a numeric colorbar here, for the sake of simplicity.
Re: Show HN: Physically accurate black hole you can put in your room
#147Earlier quoted context omitted.
Sure, but I think there's some cause/effect to consider there. The same logic would have applied in Ancient Rome, but I expect that people would have likely been less casual with their usage of such terms when they also had specific technical meanings. For example many food dishes we have retain basic naming conventions, yet have well understood meaning. In the US a customer ordering spaghetti is likely to be quite u…
> I expect that people would have likely been less casual with their usage of such terms when they also had specific technical meanings. Why would you expect that? It seems the opposite of what we see in practice. Colloquial language typically makes no concessions to technical usage. Your example works against your own position. “Spaghetti” is an Italian word, much like the Greek portmanteau that started this discuss…
I suppose the difference I see, and the motivation for change, is an issue of familiarity. Everybody knows what spaghetti is and so calling it thin noodle doesn't add much clarity for most people. By contrast many, probably the overwhelming majority, of terms that are in Latin are unfamiliar. And continuing to pile on in that domain just adds to the things people will generally be unfamiliar with.
And these are in domains that people will certainly come into contact with in their life, like healthcare, so it's not like just nitpicking over e.g. pure math's preference for having people's names attached to various mathematical constructs as opposed to something even vaguely descriptive. Very few people will ever interact with pure math in 'normal' life, so it's largely inconsequential.
I mean just imagine we were going to do things over, and in starting to name medical conditions somebody said, 'Hey I have an idea - instead of naming everything in an obvious way let's name everything using some obscure language almost nobody understands.' Nobody would really be on board with that, but we ultimately ended up in that exact scenario.
Re: Show HN: Physically accurate black hole you can put in your room
#148Earlier quoted context omitted.
Yeah the doppler in this picture is all wrong unfortunately, the underlying equation used isn't right here (they mixed up spectral radiance and radiant flux). The rendering is also done without taking into account sRGB, and its run through a function that messes with the brightness - so the brightness is really incorrect. Plus all the colours are wrong (it uses an amhot colouring function, they aren't based on anythi…
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's weird to say that colormap choice makes it not accurate.
What exactly is physically accurate here though? Because its not:
1. The relative brightness of different parts of the image
2. The colouring
3. The general relativistic effects of a black hole, other than the most basic disk warping effect
4. The relative colouring or brightness change from doppler
When you make a post about a physically accurate rendering, people usually expect it to be a decent representation of the underlying object in *some* capacity
There are of course constraints in terms of what the human eye can see and what we can portray - eg wanting to present alternative radio frequencies, highlighting different aspects of a black hole etc, which is why we make *specific* brightness and colouring map choices. That isn't a justification for making *arbitrary* choices in brightness and colouring map choices, because otherwise you could do sin(brightness * 1000) and call it physically accurate. In fact any output is an arbitrary colourmapping of a physically accurate black hole rasterisation under this definition, including a pure white square
Colour mapping and scale absolutely is very very much not an arbitrary choice, I linked elsewhere the event horizon telescope talking about this specific issue. People go to great lengths to put the work in to make physically accurate renderings, to convey accurately what you're looking at. I'm surprised to see you say that its considered arbitrary for renderings
There's a lot of room for doing visualisations to show off a specific element of a black hole, but the output here is near completely free of any physically accurate content. This is one of the more basic simulations I've seen - and that's before getting into the fact that it contains coding errors
Re: Show HN: Physically accurate black hole you can put in your room
#149Earlier quoted context omitted.
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 for the camera mode – for me, Chrome only gives one camera feed at a time, while Firefox allows both front & rear cameras. And AR + camera warping don't work together, unfortunately – browser API l…
Okay either I'm stupid or not seeing the "relativistic effects". This looks the same as on my device. I was expecting some distortion or bending of the background?
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Re: Show HN: Physically accurate black hole you can put in your room
#150Earlier quoted context omitted.
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 line-of-sight alignment for those bright jets we see across the universe. And how beaming is the dominant effect that determines the jet/quasar appearance.
I guess the fact we see any at all given the distance and small angles just emphasizes how many there are out there...
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 redshift z ~ 6? There are thousands more!
- See that well-aligned blazar jets are among strongest gamma ray (or neutrino) sources? Gamma rays/neutrinos are preferentially emitted along the jet direction, otherwise we'd seen thousands more equally strong sources.