A real-time, ray-traced simulation of a spinning (Kerr) black hole that runs entirely in your browser with WebGL2. Every pixel traces a light ray backwards from the camera and bends it through curved spacetime, producing gravitational lensing, the black shadow, and the glowing accretion disk, including the arc of the far side of the disk bent over the top and under the hole.
You can change the spin, the mass (from 1 to 66 billion solar masses), the viewing angle and the disk properties, compare the event horizon with scale rings for the Earth, the Sun and the orbit of Neptune, and drag to rotate or scroll to zoom. The disk follows the Novikov-Thorne model, with blackbody colours shifted by the Doppler effect and gravitational redshift. The method follows James et al. (2015), "Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar".