Works really well even on my old-ish smartphone (2014). WebGL is really interesting, too bad I still have yet to find the time to get a grasp of it. But blog posts like this are very inspiring!
Everyone is praising the GNOME (default) edition. Does anyone use the KDE spin? Also, how are Fedora version upgrades nowadays? I'm trying to decide between KDE neon and Fedora.
At least there's a simple equation [0] for the deflection of light rays caused by a black hole. If your background is a UV map (for example), then it should be easy to compute the distortion effect. rantonels (whose raytracer was the source of inspiration for mine) has done a realtime version [1] -- I believe this should be close to what you're talking about.
A comparison between different integrators is in the plans. It would be certainly interesting to try e.g. velocity Verlet and some other symplectic integrators.
My take on the accretion disk isn't very physically-based. It's really mostly meant as eye candy. However, the distortion (the form it takes) is physical and due to the Schwarzschild geometry.
The physical explanation of an accretion disk would be some matter that is orbiting the black hole and emitting radiation, so it makes some sense at least. https://en.wikipedia.org/wiki/Accretion_disk
That statement is indeed a bit vague. Let me elaborate:
In the process of deriving the said equations, an equation for the radial coordinate of the photon was achieved. This was identified with a classical, Newtonian system of one particle with unity mass. As the real, massless photon lives in four-dimensional spacetime and the said massive "test particle" lives in three-dimensional space, these systems just can't be dynamically the same (in spacetime, the massive particle would take a timelike curve).
To reword the statement, the derived "equation of motion" will yield the same trajectory in the spacelike components (x, y, z), but possibly with a different parametrization - in the classical system, we're integrating the equations of motion with respect to the time. However, this has nothing to do with the "coordinate time" of the four-vectors nor the proper time of the particle (for the photon, proper time doesn't even make sense).
Hope this helps! You could also see [0] for an alternative take on this derivation. I will try and clarify my article a bit as well.
Maybe in the future, and in small resolution. Right now the renderer doesn't have any animation functionality, but this is definitely something I've been considering.
I thought I would share this little writeup on a project I'm quite proud of. The code can be found on GitHub [0]. This article is mostly about the implementation of the simulation in Haskell. I've also written another article [1] on the physics of the simulation. It should be approachable even for those without any general relativity background.
Funny how the X11 "Fixed" bitmap font [0] is chosen as the default font on my system. This appears to be caused by 'fixed' being set as a fallback font instead of 'monospace', which, on most systems, is an alias for the default monospace font which is usually an antialiased one.