quimbot/docs/gallery/spirograph.html at main · milwrite/quimbot · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <link rel="icon" type="image/png" href="../favicon.png">
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no, viewport-fit=cover">
<title>Spirograph</title>
<style>
* { margin: 0; padding: 0; box-sizing: border-box; }
body { background: #050510; display: flex; align-items: center; justify-content: center;
       height: 100dvh; overflow: hidden; }
canvas { display: block; touch-action: none; }
#ui {
  position: fixed; bottom: max(18px, env(safe-area-inset-bottom));
  left: 50%; transform: translateX(-50%);
  display: flex; gap: 14px; align-items: center; flex-wrap: wrap; justify-content: center;
  background: rgba(5,5,20,.7); border: 1px solid #334; border-radius: 8px; padding: 8px 14px;
}
#ui label { color: #99c; font: 12px/1.6 monospace; display: flex; align-items: center; gap: 6px; }
#ui input[type=range] { width: 90px; accent-color: #c8f; }
#hint { position: fixed; top: 50%; left: 50%; transform: translate(-50%,-50%);
        color: #445; font: 13px monospace; pointer-events: none; }
#back {
  position: fixed; top: max(16px, env(safe-area-inset-top)); left: max(16px, env(safe-area-inset-left));
  background: rgba(0,0,.1,.65); color: #aab; font: 13px monospace;
  padding: 6px 12px; border: 1px solid #334; border-radius: 4px; text-decoration: none;
}
#back:hover { color: #fff; border-color: #99c; }
#label { position: fixed; top: max(16px, env(safe-area-inset-top)); right: max(16px, env(safe-area-inset-right));
         color: #445; font: 11px monospace; }
</style>
</head>
<body>
<canvas id="c"></canvas>
<div id="ui">
  <label>speed <input id="spd" type="range" min="1" max="8" step="0.5" value="3"></label>
  <label>pen   <input id="pen" type="range" min="0.2" max="1.8" step="0.05" value="1.0"></label>
</div>
<a id="back" href="../">← gallery</a>
<div id="label"></div>

<script>
'use strict';
const canvas  = document.getElementById('c');
const ctx     = canvas.getContext('2d');
const spdEl   = document.getElementById('spd');
const penEl   = document.getElementById('pen');
const labelEl = document.getElementById('label');

const inIframe = window.self !== window.top;
if (inIframe) {
  document.getElementById('ui').style.display   = 'none';
  document.getElementById('back').style.display = 'none';
  document.getElementById('label').style.display = 'none';
}

// ── Spirograph presets (p outer teeth, q inner teeth)  ───────────────────────
// hypotrochoid: r = R*q/p, period = 2π·p
const PRESETS = [
  { p:  5, q:  3, hue: 280 }, // 5-petal rose
  { p:  7, q:  2, hue:  50 }, // 7 outer petals
  { p:  7, q:  3, hue: 160 },
  { p:  8, q:  3, hue: 200 },
  { p: 11, q:  4, hue: 320 },
  { p: 13, q:  5, hue:  20 },
  { p: 17, q:  7, hue: 180 },
  { p: 19, q:  6, hue: 260 },
  { p: 21, q:  8, hue: 100 },
  { p: 24, q:  7, hue: 340 },
];

let W, H, R;    // canvas dims + outer radius

function resize() {
  W = canvas.width  = window.innerWidth;
  H = canvas.height = window.innerHeight;
  R = Math.min(W, H) * 0.42;
}
resize();
window.addEventListener('resize', () => { resize(); startNew(); });

// ── state ─────────────────────────────────────────────────────────────────────
let preset, r, d, period, t, hue0, phase;
let trailBuf = [];   // [{x,y,h}] — accumulated path for redraw
let state;           // 'drawing' | 'pause' | 'fade'
let pauseTimer;

function gcd(a, b) { return b === 0 ? a : gcd(b, a % b); }

function pickPreset(skip) {
  let idx;
  do { idx = Math.floor(Math.random() * PRESETS.length); } while (PRESETS[idx] === skip);
  return PRESETS[idx];
}

function startNew() {
  preset = pickPreset(preset);
  const { p, q } = preset;
  const g = gcd(p, q);
  const pp = p / g, qq = q / g;
  r      = R * qq / pp;
  const d_ratio = parseFloat(penEl.value);
  d      = r * d_ratio;
  period = 2 * Math.PI * pp;   // full closure period
  t      = 0;
  hue0   = preset.hue;
  phase  = Math.random() * 2 * Math.PI;
  trailBuf = [];
  state  = 'drawing';
  // clear canvas
  ctx.fillStyle = '#050510';
  ctx.fillRect(0, 0, W, H);
  if (!inIframe) labelEl.textContent = `p=${pp}  q=${qq}`;
}

// ── hypotrochoid point ────────────────────────────────────────────────────────
function htPoint(tt) {
  const Rr = R - r;
  const ratio = Rr / r;
  return {
    x: W / 2 + Rr * Math.cos(tt) + d * Math.cos(ratio * tt),
    y: H / 2 + Rr * Math.sin(tt) - d * Math.sin(ratio * tt),
  };
}

// ── draw trail array ──────────────────────────────────────────────────────────
function drawFull(alpha) {
  if (trailBuf.length < 2) return;
  for (let i = 1; i < trailBuf.length; i++) {
    const a = trailBuf[i - 1], b = trailBuf[i];
    ctx.beginPath();
    ctx.moveTo(a.x, a.y);
    ctx.lineTo(b.x, b.y);
    const prog = i / trailBuf.length;
    const hue  = (hue0 + prog * 240) % 360;
    ctx.strokeStyle = `hsla(${hue},90%,65%,${alpha.toFixed(3)})`;
    ctx.lineWidth   = 1.5;
    ctx.stroke();
  }
}

// ── main loop ─────────────────────────────────────────────────────────────────
const STEPS_PER_FRAME = 800;          // sub-steps per frame to hit speed
let   STEP_SIZE       = 0.004;        // t increment per sub-step

function frame() {
  requestAnimationFrame(frame);

  const speed = parseFloat(spdEl.value);
  STEP_SIZE   = 0.003 * speed;

  if (state === 'drawing') {
    const prevPt = htPoint(t);
    let steps = Math.ceil(speed * 80);
    for (let i = 0; i < steps; i++) {
      t += STEP_SIZE;
      if (t >= period) { t = period; state = 'pause'; pauseTimer = performance.now(); break; }
      const pt = htPoint(t);
      const prog = t / period;
      const h    = (hue0 + prog * 240) % 360;
      ctx.beginPath();
      ctx.moveTo(trailBuf.length ? trailBuf[trailBuf.length-1].x : prevPt.x,
                 trailBuf.length ? trailBuf[trailBuf.length-1].y : prevPt.y);
      ctx.lineTo(pt.x, pt.y);
      ctx.strokeStyle = `hsla(${h},90%,65%,0.85)`;
      ctx.lineWidth   = 1.6;
      ctx.stroke();
      trailBuf.push({ x: pt.x, y: pt.y });
    }

  } else if (state === 'pause') {
    const elapsed = performance.now() - pauseTimer;
    if (elapsed > 1800) { state = 'fade'; pauseTimer = performance.now(); }

  } else if (state === 'fade') {
    const elapsed = performance.now() - pauseTimer;
    const alpha   = Math.max(0, 1 - elapsed / 600);
    ctx.fillStyle = '#050510';
    ctx.fillRect(0, 0, W, H);
    drawFull(alpha);
    if (alpha <= 0) startNew();
  }
}

// ── pointer — click to skip to next ──────────────────────────────────────────
canvas.addEventListener('pointerdown', () => startNew());

startNew();
requestAnimationFrame(frame);
</script>
</body>
</html>