This is a black hole that I created in HLSL.

Conceptually, the process isn't too terrifyingly complicated. It's just raymarching light forward with a nearby gravity well that can absorb said light.

The accretion disk is mostly an artistic imitation of sorts. I initially thought it might be cool to include actual particle simulations for it, but ultimately decided against that idea. Too difficult to account for if I want the accretion disk to stay a consistent shape. Instead, I went with a simple flattened torus. As the light marches forward and "interacts" with this torus (aka gets close in distance to it), blazing orange and yellow colors are added to it.

The black hole itself is just a matter of making the marched light have a tendency to "bend" towards the black hole, based on the inverse square law. If the light manages to slip past the event horizon radius it ceases to contribute anything to the final results.