#The creative potential of random

Ben Swift, School of Cybernetics

COMP1720 Guest Lecture 2017

#synopsis

• randomness: highlights from history
• different types of randomness
• mapping: using randomness effectively

#randomness in music has a long history

musikalisches würfelspiel (18th century)

aleatoric music (20th century)

some of our labs have explored randomness in various forms

#types of randomness

not all randomness is created equal

but this isn’t a maths lecture

#three useful types for artists

1. uniform — random([min], [max])
2. gaussian — randomGaussian()
3. discrete — random(choices) (Array version)

#uniform random numbers

start with two numbers (min and max)

picks any number between those two numbers

all numbers in the range are equally likely

this last point is the key attribute of random numbers

#gaussian random numbers

picks a number around some middle point

numbers closer to that middle point are more likely than ones further away

named after Carl Friedrich Gauss

also known as: normal distribution, bell curve, etc.

#discrete random variables

sometimes there are a fixed number of outcomes, either equally likely or some more likely than others

e.g. coin toss, roll of the dice, football match

let’s look at the reference for random() again — if passed one parameter which is an array, the return value will be one of the elements of the array, selected at random (all equally likely)

#different likelihoods, technique 1

if you want some outcomes to happen more often than others, add multiple identical elements to the array (think about why this works?)

var loadedDice = [1, 2, 2, 2, 2, 3, 4, 5, 6];
var roll = random(loadedDice);

#different likelihoods, technique 2

if you want one thing to happen e.g. 10% of the time, and something else the other 90%

1. use random(100) to get a random number between 0 and 100
2. if the result is less than 10, do the first thing; otherwise do the other

#mapping: using randomness effectively

mapping (I know the word “map” is overloaded in programming) here means what do you do with the randomness

in my livecoding I use random numbers to control or modulate: pitch, loudness, duration, rhythm, timbre, and more

#mapping random numbers in your sketches

think about how (and what kinds) of randomness you could use to control: position, size/shape, colour/transparency, stroke/fill, etc.

what’s the right balance between predictability and surprise?

choosing where to use randomness, where not to use it, and what type: this is where the art happens

#re-creating the random pixels image

loadPixels();
for (var i = 0; i < pixels.length; i++) {
  if (random() < 0.5) pixels[i] = 0;
  else pixels[i] = 255;
}
updatePixels();