Renders a grid of tiny cells with per-frame varying opacity using deterministic pseudo-random values based on (index * frame) % prime, creating a subtle flickering film grain effect. Overlay this on any scene to add analog warmth and cinematic texture.
Grain density, opacity range, and cell size are configurable. The effect is intentionally subtle (0.02-0.08 opacity) to add texture without overwhelming content. Deterministic pseudo-random ensures frame-perfect reproducibility.