Randomization helpers

A scene that re-rolls its parameters on a beat gets old fast if every roll is equally likely — you end up with the extreme settings as often as the tasteful ones, and the whole thing reads as noise. What you usually want is mostly restrained with the occasional big move.

These are the pickers for that.

function randFromList(list, n) {
    // no n → one pick; n → array of n picks
    if (typeof n != 'number')
        return list[Math.floor(Math.random() * list.length)];
    var r = [];
    for (var i = 0; i < n; i++)
        r.push(list[Math.floor(Math.random() * list.length)]);
    return r;
}

// multiplying two randoms biases hard toward index 0
function randFromListExp(list) {
    return list[Math.floor(Math.random() * Math.random() * list.length)];
}

function randNegPos()    { return Math.floor(Math.random() * 2) * 2 - 1; }   // -1 or 1
function rand2PIsigned() { return Math.random() * Math.PI * 2 - Math.PI; }   // -2π..2π

randFromListExp is the one worth understanding. Multiplying two independent uniform randoms gives a distribution crushed toward zero — the product is below 0.25 about 60% of the time. So if you order your list from tame to extreme, you get the subtle options most of the time and the wild one rarely, without writing an explicit weight table.

randNegPos flips a spin or scroll direction. rand2PIsigned gives a random angle in either direction, which is exactly what a camera goal wants.

Usage

var speeds  = [0.2, 0.5, 1.0, 2.0, 8.0];   // tame → extreme, order matters
var palettes = ['warm', 'cool', 'mono'];

function setup() {
    onOffToOn('syn_BassHits', 'reroll');
}

function reroll() {
    setUniform('speed', randFromListExp(speeds));   // usually 0.2, rarely 8.0
    setUniform('spin',  randNegPos());
    cam_rd.smooth();                                 // uses rand2PIsigned internally
}

Notes

• randFromListExp only works if the list is sorted by intensity. It weights by position, not by value — an unordered list just gets an arbitrary bias.
• Want a gentler curve? Math.random() alone is flat, two multiplied is steep. Math.pow(Math.random(), 1.5) sits between them if you need to dial it in.
• randFromList(list, n) can return the same item twice — it samples with replacement. For “pick 3 distinct” you need a shuffle instead.
• Re-rolling on every bass hit is usually too often. Gate it behind a counter or a beat multiple, or the scene never holds still long enough to look like anything.
• Rolling in setup() gives each launch a personality — a cheap way to make a scene feel less deterministic without any runtime cost.