Ray tracing of a black hole and its shadow
Light rays follow the curved space-time and thus create a distorted image of an accretion disk.
https://www.youtube.com/watch?v=bd4m217y6j0
In April 2019, the first "image" of a black hole was published by the Event Horizon Telescope (EHT) scientists. In cooperation with the relativistic astrophysics group led by Luciano Rezzolla a short movie explaining how the shadow of a black hole emerges and how the distorted view of a thin accretion disk looks like was created.