Ordered dithering
A dithering method that decides each pixel's rounding against a fixed threshold matrix rather than spreading the error onward, giving a characteristic cross-hatched look.
Ordered dithering tiles a small threshold matrix — usually a Bayer matrix — across the image and compares each pixel's value to the threshold at its position. Above it, a light dot is placed; below, a dark one; the sum fools the eye into seeing more shades than the palette holds. Unlike Floyd–Steinberg and other dithering that push the quantisation error on to neighbouring pixels, the method is stateless: each pixel depends only on its coordinates.
That makes it fast, trivially parallel and perfectly reproducible — the same matrix yields the same pattern every frame, with no shimmer between frames. The cost is the obvious cross-hatch or checkerboard texture, a 1980s aesthetic that has since become a deliberate style. Modern shaders use it for cheap transparency via alpha testing, for breaking up colour banding in smooth gradients, and for smoke and shadows where a true alpha value would be too expensive.