Comment by aplavin
6 hours 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'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
> 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 certain about. This is reproduced accurately in all modes, up to the fundamental technical constraints of the browser environment. Gravitational redshift is another one, and it's also reflected.
Things like the precise matter configuration in the disk (and correspondingly its radial brightness profile) are much less well known, and are less fundamental for black holes as objects. This part is represented in a simplified way – thin disk, with a reasonable-shape analytic function defining radial emissivity distribution.
As for colormapping: 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. Having a preference for different color schemes is a matter of taste; suggesting a linear intensity->pixel mapping is a reasonable feature request, but far from a bug or inaccuracy.