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aplavin 10 hours 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 :) And also, even on a phone with two cameras, they only cover a part of sphere – while a real black hole would bend light coming from all 4pi directions. Some simplification is generally required ("the map is not the territory") and I don't see "simplified" as being opposite to "accurate".

Colormap choice: it can be a useful mode to show proper linear power -> linear perceived brightness mapping – true! But that's only one of many possible choices, and scales like logarithmic are very common in scientific images.

20k 10 hours ago | parent | next [-]

>I don't see "simplified" as being opposite to "accurate".

Are black hole accretion disks generally red in real astrophysical cases?

They're most accurately represented as being blue. Red is fine for visualisations because it looks cool (which is fine!), but blue is the physically accurate colour. Visualisations claiming to be accurate like this presenting red black holes is becoming an increasingly large science communication problem

The way that the colour and brightness are mapped together is also not correlated correctly, and some of the equations just aren't right. The doppler isn't correct at all here, partly because its simulated incorrectly (with the camera problems), and partly because the mapping done at the end doesn't correlate to any reasonable brightness

Stuff like this: Its not accurate at all. It isn't simplified, its just wrong - which is totally fine for a visualisation, if that's the intent. But:

>scales like logarithmic are very common in scientific images.

Sure. What scale are you using for the doppler brightness here? Because as far as I can tell, its a piecewise mapping of the form ~pow(x, 2.2), after being run through a non smooth function `afmhot` - a function which doesn't have a linear brightness response. So the brightness in this image doesn't really correspond to anything related to doppler or brightness, and the colour also doesn't correspond to anything involving colour (or the doppler). The entire image's look is basically accidental

Here's a specific comment from the event horizon telescope talking about exactly this problem with specifically the afmhot transform being used, because its important for visualisation:

https://github.com/achael/eht-imaging/issues/85

Which shows some of the problems here

EugeneOZ 9 hours ago | parent | prev | next [-]

“Physically accurate” indeed raises the bar significantly.

You’ve already done great work here. That said, the feedback seems to come from someone who spent considerable time analyzing your work. Even if only a few of the suggestions are ultimately valuable, that’s still a meaningful contribution and worth considering.

aplavin 2 hours ago | parent [-]

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.

7bit 4 hours ago | parent | prev [-]

Always funny when people claim that scientific term apply to their software and then disregard any founded criticism in a non scientific way.

20k 38 minutes ago | parent [-]

Its frustrating because these issues are all fixable, and some of them are just bugs, but there's a mentality in this kind of science communication that ehh it doesn't matter because its just for the public. This does a real disservice to what people are trying to actually achieve in educating the public. Its also, unsurprisingly, a lot of hard work and validation to get from visualisation-grade, to physically accurate, and its a lot easier to not do that

aplavin 30 minutes ago | parent | next [-]

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 way.

andrecarini a minute ago | parent [-]

You seem more interested in putting effort downplaying criticism and upholding the optics of "scientifically accurate thing from researcher in big name university" than actually putting effort on making the thing good and using the amazing feedback you got

7bit 14 minutes ago | parent | prev [-]

I don't understand what you are saying.

The only criticism is to call that accurate, when it's simplified. OP ist defending the use of accurate with dumb arguments. The fix would simply be to not claim "accurate" and continue to provide a probably great visualisation (idk, haven't looked at it)