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11. Randomness and noise

Random numbers

Helper What it gives
f.random(high) / f.random(low, high) a random decimal number in the range
f.random_gaussian(mean, sd) a number from a bell curve: most near mean, about two thirds within sd of it
f.random_choice(items) one item from a list, tuple or string
f.random_seed(n) makes all of the above repeat exactly — the same "random" picture every run

Confetti

Bell curve and choices

Noise: smooth randomness

f.random() jumps anywhere every time. f.noise(x) gives a number from 0 to 1 that changes smoothly as x changes — like hills instead of static. Walk slowly along it (small steps in x) for gentle change, quickly for rough change.

Helper What it does
f.noise(x), f.noise(x, y), f.noise(x, y, z) Smooth value from 0 to 1; with two inputs, a smooth pattern across the window; the third is often time
f.noise_seed(n) Picks the pattern, so it repeats every run. The same seed gives the same values as p5.js
f.noise_detail(octaves, falloff) Fewer octaves (layers) is smoother and faster; the default is 4 
import funground as f


def setup():
    f.size(640, 200)
    f.noise_seed(1)


def draw():
    f.background("white")
    f.no_fill()
    f.stroke("tomato")
    f.stroke_width(3)
    f.begin_shape()
    for x in range(0, 641, 4):
        f.vertex(x, 20 + f.noise(x * 0.01, f.frame_count * 0.01) * 160)
    f.end_shape()


f.run()

Noise

Speed. Each noise() call takes a few microseconds, so about 1,500 calls per frame keep a sketch at 60 frames per second. For big textures, use fewer octaves or bigger tiles.

See also

Try it

  1. Scatter 200 small circles at random places. Add f.random_seed(1) in setup(). What changes?
  2. Give each circle a random colour with f.random_choice([...]) from a list of colour names.
  3. Draw a wavy line with f.noise(), then move it along by adding f.frame_count to the noise input.

Next: 12. Useful maths