73 lines
2.1 KiB
JavaScript
73 lines
2.1 KiB
JavaScript
import {Ticker, withResolvers} from '@/util/promise.js';
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const Modulators = {
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flat: () => 0.5,
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random: () => Math.random(),
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sawtooth: (unit) => unit,
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sine: (unit) => 0.5 * (1 + Math.sin(unit * Math.PI * 2)),
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square: (unit) => (unit < 0.5 ? 0 : 1),
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triangle: (unit) => 2 * Math.abs(((unit + 0.75) % 1) - 0.5),
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};
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export default function lfo(object, properties) {
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const oscillators = {};
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const promises = [];
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for (const key in properties) {
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const property = properties[key];
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const oscillator = {
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count: Infinity,
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elapsed: 0,
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offset: 0,
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...property,
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};
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if (!('median' in oscillator)) {
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oscillator.median = oscillator.magnitude / 2;
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}
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if (!oscillator.modulators) {
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oscillator.modulators = [Modulators.triangle];
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}
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else {
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const {modulators} = oscillator;
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for (const i in modulators) {
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if ('string' === typeof modulators[i]) {
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modulators[i] = Modulators[modulators[i]];
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}
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}
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}
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oscillator.low = oscillator.median - oscillator.magnitude / 2;
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({promise: oscillator.promise, resolve: oscillator.stop} = withResolvers());
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oscillator.promise.then(() => {
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delete oscillators[key];
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});
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promises.push(oscillator.promise);
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oscillators[key] = oscillator;
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}
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let stop;
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const promise = new Ticker(
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(resolve) => {
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stop = resolve;
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Promise.all(promises).then(resolve);
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},
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(elapsed) => {
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for (const key in oscillators) {
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const oscillator = oscillators[key];
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oscillator.elapsed += elapsed;
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if (oscillator.elapsed >= oscillator.frequency) {
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if (0 === --oscillator.count) {
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oscillator.stop();
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return;
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}
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oscillator.elapsed = oscillator.elapsed % oscillator.frequency;
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}
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const x = (oscillator.offset + (oscillator.elapsed / oscillator.frequency)) % 1;
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let y = 0;
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for (const modulator of oscillator.modulators) {
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y += modulator(x);
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}
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object[key] = oscillator.low + oscillator.magnitude * (y / oscillator.modulators.length);
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}
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},
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);
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return {stop, oscillators, promise};
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}
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