What do black holes look like?

This article explores how to simulate the visual appearance of a black hole by calculating photon trajectories in a Schwarzschild metric. It explains the physics of gravitational lensing, where a black hole's gravity bends light from background scenes, and describes a method to efficiently compute the mapping from camera angles to background angles. The approach involves tracing rays backward from the camera to determine where they end up, producing distorted images of the far-off background. The article covers the mathematical setup, the use of the Schwarzschild metric, and the computational technique to generate the angle-to-angle mapping function, omitting gravitational redshift for simplicity.