Harmonograph by alexmacy

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Harmonograph</title>
<style>
  body {
    font-family: Monospace;
    margin:0px;
  }
  canvas {
    position: absolute; 
    top: 0px; 
    left: 0px; 
    z-index: -2;
  }
  details {
    position: absolute;
    left: 10px;
    top: 10px;
  }
  .left, .right, details{
    z-index: 9;
  }
  .left {
    display: flex;
    flex-flow: column wrap;
  }
  .oscillator {
    background-color: rgba(255, 255, 255, .75);
    box-shadow: 0px 0px 5px rgb(200, 200, 200);
    margin: 5px;
    padding: 5px;
  }
  h3 {
    margin: 5px;
  }
  .summary {
    padding: 5px;    
  }
  .controller {
    background-color: rgba(255, 255, 255, .75);
    box-shadow: 0px 0px 5px rgb(200, 200, 200);
    margin: 5px;
    padding: 10px;
  }
</style>

<body>
<template class="controller-template">
  <div class="controller">
    <h3 class="title"></h3>
    <div class="frequency"><div></div>
      <input type="range" min="1" max="30" step="1" name="freq">
    </div>
    <div class="damping"><div></div>
      <input type="range" min="0.001" max="0.05" step="0.0001" value="0.001" name="damping">
    </div>
    <div class="amplitude"><div></div>
      <input type="range" value="100" name="amp">
    </div>
    <div class="phase"><div></div>
      <input type="range" value="0" name="phase">
    </div>
    <div class="offset">Phase: <text></text>°</div>
    <button class="phase-reset">Reset Phase</button>
  </div>
</template>

<div class="controller-container">
  <details open>
    <summary class="oscillator summary">Oscillators</summary>
    <div class="left"></div>
  </details>
</div>

<canvas></canvas>

<script>
const canvas = document.querySelector('canvas');
canvas.setAttribute('width',innerWidth);
canvas.setAttribute('height',innerHeight);

const canvasCtx = canvas.getContext("2d");
canvasCtx.fillStyle = 'rgb(255, 255, 255)';
canvasCtx.strokeStyle = '#003300';
canvasCtx.lineWidth = .5;

const width = innerWidth;
const height = innerHeight;

let dataLength = 500;
let paused = false;

// set dimension for the left side flex container
document.querySelector(".left").style.height = innerHeight * .9 + "px";

const template = document.querySelector('.controller-template')
    .content.querySelector(".controller");

const oscVals = [
  {key: "x1", f: 1, d: 0.004, p: 0, a: 100}, 
  {key: "x2", f: 3, d: 0.007, p: 0, a: 100}, 
  {key: "y1", f: 5, d: 0.008, p: 8, a: 100}, 
  {key: "y2", f: 7, d: 0.019, p: 24, a: 100},
]

const oscs = oscVals.map(Oscillator);

renderLoop()

function Oscillator(vals) {
  const self = {};

  const newOsc = document.importNode(template, true);
  newOsc.querySelector(".title").innerHTML = vals.key;
  
  const [fText, fInput] = newOsc.querySelector(".frequency").children;
  const [dText, dInput] = newOsc.querySelector(".damping").children;
  const [aText, aInput] = newOsc.querySelector(".amplitude").children;
  const [pText, pInput] = newOsc.querySelector(".phase").children;

  self.freq = vals.f;
  self.damping = vals.d;
  self.amp = vals.a;
  self.phase = vals.p;
  self.offsetText = newOsc.querySelector(".offset text");
  self.offset = 0;

  fInput.value = self.freq;
  dInput.value = self.damping;
  aInput.value = self.amp;
  pInput.value = self.phase;

  fInput.oninput = updateOsc;
  dInput.oninput = updateOsc;
  aInput.oninput = updateOsc;
  pInput.oninput = updateOsc;

  newOsc.querySelector(".phase-reset").onclick = function() {
    pInput.value = 0;
    self.phase = 0;
    self.offset = 0;
    t = 0;
    updateOsc();
  }

  self.getVal = function(t = 0) {
    return (
      self.amp * 
      Math.sin(t * self.freq + self.offset * Math.PI*2) * 
      Math.exp(-self.damping * t)
    );
  }

  updateOsc();

  document.querySelector(".left").appendChild(newOsc);

  return self;

  function updateOsc() {   
    if (this.name) self[this.name] = Number(this.value);

    fText.innerHTML = "Frequency: " + self.freq + "00Hz";
    dText.innerHTML = "Damping: " + self.damping;
    aText.innerHTML = "Amplitude: " + self.amp + "%";
    pText.innerHTML = "Phase Rate: " + self.phase + "%";

    if (paused) renderLoop();
  }
}

function harmonograph(n, offset, controls) {
  let val = 0;
  for (let i of controls) val += oscs[i].getVal(n);
  return val * 1.5 + offset/2;
}

function renderLoop() {
  if (paused) paused = false;

  for (let osc of oscs) {
    osc.offset = (osc.offset + osc.phase/5000) % 1;
    osc.offsetText.innerHTML = Math.round(osc.offset * 360);
  }

  draw();

  requestAnimationFrame(renderLoop);
}

function draw() {
  canvasCtx.fillRect(0, 0, innerWidth, innerHeight);
  canvasCtx.beginPath();
  
  let i = dataLength;
  
  canvasCtx.moveTo(
    harmonograph(i, innerWidth, [0, 1]), 
    harmonograph(i, innerHeight, [2, 3])
    );

  while (i >= 0) {
    canvasCtx.lineTo(
      harmonograph(i, innerWidth, [0, 1]), 
      harmonograph(i, innerHeight, [2, 3])
      );
    i -= .01;
  }
  canvasCtx.stroke();

}
</script>