Scrub the timestep slider to watch an image materialise from pure noise (T=1000) to a clean digit (T=0) via the cosine noise schedule.
What the U-Net sees: Almost pure noise — the U-Net sees nothing useful yet
Cosine schedule: ᾱ_t = cos(0.5π·t/T)². At T=0 the image is fully clean (ᾱ=1); at T=1000 it is pure noise (ᾱ≈0).