The Forward Process — Destroying Images with Noise, Carefully
Diffusion models begin with the only part of the pipeline that involves no learning at all: a fixed, mechanical procedure that gradually turns any image into pure static. It seems almost too simple to matter — yet every design choice in it (Gaussian noise, small steps, a schedule, a closed-form shortcut) is load-bearing for everything the model later learns. Understanding the destruction is half of understanding the generation.
The forward process is a fixed Markov chain that turns any image into pure Gaussian static — no learning anywhere. Why Gaussian noise (closure), what the noise schedule allocates (practice time across corruption levels), the closed-form jump that makes training random-access, and the known endpoint generation starts from.