08完成した模様が回るターンテーブル場面

<main class="stage">
<div class="sp8 is-demo" id="sp8Root" tabindex="0">
  <canvas class="sp8__canvas" id="sp8Canvas" width="480" height="300"></canvas>
  <p class="sp8__caption">曲線を描き終えた後、キャンバス全体を回転変換でゆっくり回し、模様の対称軸を通過するたびに重なって見える錯視が生まれ、回転角度の値がそのリズムを決める</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-paper);

.sp8 {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $stage-paper;
}

.sp8__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.sp8__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 78%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 247, 230, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .sp8__caption { font-size: 10px; padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .sp8 { cursor: default; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sp8 {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #ffffff;
}

.sp8__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.sp8__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 78%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .sp8__caption {
    font-size: 10px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sp8 {
    cursor: default;
  }
}

(function () {
  // 기법: 완성된 무늬는 한 번만 계산해 배열에 담아두고, 매 프레임 회전 각도만 바꿔 다시
  // 그린다. 그 위에 독립된 타이머로 광택 띠를 원판 클립 안에서 쓸어 지나가게 겹친다.
  var root = document.getElementById('sp8Root');
  var canvas = document.getElementById('sp8Canvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  var CALC_DIM = 200;
  var GEAR_RING_TEETH = 48;
  var GEAR_ROLL_TEETH = 18;
  var PEN_TIP_RATIO = 0.58;
  var TOOTH_UNIT = 1.6;
  var SEGMENTS_PER_TURN = 180;
  var ROTATE_SPEED = (2 * Math.PI) / 9;
  var GLOSS_SWEEP_SECONDS = 3.4;
  var DISC_RATIO = 0.82;

  function gcd(a, b) { while (b) { var t = b; b = a % b; a = t; } return a; }
  var g = gcd(GEAR_RING_TEETH, GEAR_ROLL_TEETH);
  var TURNS = GEAR_ROLL_TEETH / g;
  var AXIS_COUNT = GEAR_RING_TEETH / g;

  var R = GEAR_RING_TEETH * TOOTH_UNIT;
  var r = GEAR_ROLL_TEETH * TOOTH_UNIT;
  var d = r * PEN_TIP_RATIO;
  var K = (R - r) / r;

  var pathData = (function () {
    var maxT = 2 * Math.PI * TURNS;
    var step = (2 * Math.PI) / SEGMENTS_PER_TURN;
    var pts = [];
    for (var t = 0; t <= maxT; t += step) {
      pts.push({
        x: (R - r) * Math.cos(t) + d * Math.cos(K * t),
        y: (R - r) * Math.sin(t) - d * Math.sin(K * t)
      });
    }
    return pts;
  })();
  var patternRadius = R + d;

  var cw = 480, ch = 300, scale = 1, cx = 240, cy = 150;
  function fit() {
    var rect = wrap.getBoundingClientRect();
    cw = Math.max(1, Math.round(rect.width));
    ch = Math.max(1, Math.round(rect.height));
    canvas.width = cw; canvas.height = ch;
    var targetDiscPx = Math.min(cw, ch) / 2 * DISC_RATIO;
    scale = targetDiscPx / (patternRadius * 1.08);
    cx = cw / 2; cy = ch / 2;
  }

  function render(rot, sweepProgress) {
    ctx.fillStyle = '#ffffff';
    ctx.fillRect(0, 0, cw, ch);

    var discR = patternRadius * scale * 1.08;

    var plate = ctx.createRadialGradient(cx, cy, discR * 0.15, cx, cy, discR);
    plate.addColorStop(0, '#fff7e6');
    plate.addColorStop(0.75, '#f4ead4');
    plate.addColorStop(1, '#e6d8ba');
    ctx.beginPath();
    ctx.arc(cx, cy, discR, 0, Math.PI * 2);
    ctx.fillStyle = plate;
    ctx.fill();

    ctx.save();
    ctx.translate(cx, cy);
    ctx.rotate(rot);
    ctx.beginPath();
    for (var i = 0; i < pathData.length; i += 1) {
      var p = pathData[i];
      var sx = p.x * scale, sy = p.y * scale;
      if (i === 0) { ctx.moveTo(sx, sy); } else { ctx.lineTo(sx, sy); }
    }
    ctx.closePath();
    ctx.strokeStyle = 'rgba(10,79,232,.82)';
    ctx.lineWidth = Math.max(1.6, scale * 0.022);
    ctx.lineJoin = 'round';
    ctx.stroke();
    ctx.restore();

    ctx.save();
    ctx.beginPath();
    ctx.arc(cx, cy, discR, 0, Math.PI * 2);
    ctx.clip();
    var bandCenter = (sweepProgress * 2 - 0.5) * discR * 2.2;
    ctx.translate(cx, cy);
    ctx.rotate(-0.5);
    var glossGrad = ctx.createLinearGradient(bandCenter - discR * 0.35, 0, bandCenter + discR * 0.35, 0);
    glossGrad.addColorStop(0, 'rgba(255,255,255,0)');
    glossGrad.addColorStop(0.5, 'rgba(255,255,255,.32)');
    glossGrad.addColorStop(1, 'rgba(255,255,255,0)');
    ctx.fillStyle = glossGrad;
    ctx.fillRect(bandCenter - discR * 0.4, -discR * 1.5, discR * 0.8, discR * 3);
    ctx.restore();
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  fit();

  if (reduce) {
    root.classList.remove('is-demo');
    render(0, 0.5);
  } else {
    var startTs = null;
    function tick(ts) {
      if (startTs === null) startTs = ts;
      var elapsed = (ts - startTs) / 1000;
      var rot = elapsed * ROTATE_SPEED;
      var sweepProgress = (elapsed % GLOSS_SWEEP_SECONDS) / GLOSS_SWEEP_SECONDS;
      render(rot, sweepProgress);
      requestAnimationFrame(tick);
    }
    window.addEventListener('resize', fit);
    requestAnimationFrame(tick);
  }
})();

import { useEffect, useRef } from "react";
import styles from "./SpiroSceneCurveTurnTable.module.scss";

type Pt = { x: number; y: number };

export default function SpiroSceneCurveTurnTable() {
  const rootRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    if (!root || !canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const wrap = canvas.parentElement as HTMLElement;

    const CALC_DIM = 200;
    const GEAR_RING_TEETH = 48;
    const GEAR_ROLL_TEETH = 18;
    const PEN_TIP_RATIO = 0.58;
    const TOOTH_UNIT = 1.6;
    const SEGMENTS_PER_TURN = 180;
    const ROTATE_SPEED = (2 * Math.PI) / 9;
    const GLOSS_SWEEP_SECONDS = 3.4;
    const DISC_RATIO = 0.82;

    function gcd(a: number, b: number): number { while (b) { const t = b; b = a % b; a = t; } return a; }
    const g = gcd(GEAR_RING_TEETH, GEAR_ROLL_TEETH);
    const TURNS = GEAR_ROLL_TEETH / g;

    const R = GEAR_RING_TEETH * TOOTH_UNIT;
    const r = GEAR_ROLL_TEETH * TOOTH_UNIT;
    const d = r * PEN_TIP_RATIO;
    const K = (R - r) / r;

    const pathData: Pt[] = (function () {
      const maxT = 2 * Math.PI * TURNS;
      const step = (2 * Math.PI) / SEGMENTS_PER_TURN;
      const pts: Pt[] = [];
      for (let t = 0; t <= maxT; t += step) {
        pts.push({
          x: (R - r) * Math.cos(t) + d * Math.cos(K * t),
          y: (R - r) * Math.sin(t) - d * Math.sin(K * t)
        });
      }
      return pts;
    })();
    const patternRadius = R + d;

    let cw = 480, ch = 300, scale = 1, cx = 240, cy = 150;
    function fit() {
      const rect = wrap.getBoundingClientRect();
      cw = Math.max(1, Math.round(rect.width));
      ch = Math.max(1, Math.round(rect.height));
      canvas!.width = cw; canvas!.height = ch;
      const targetDiscPx = Math.min(cw, ch) / 2 * DISC_RATIO;
      scale = targetDiscPx / (patternRadius * 1.08);
      cx = cw / 2; cy = ch / 2;
    }

    function render(rot: number, sweepProgress: number) {
      ctx!.fillStyle = "#ffffff";
      ctx!.fillRect(0, 0, cw, ch);

      const discR = patternRadius * scale * 1.08;

      const plate = ctx!.createRadialGradient(cx, cy, discR * 0.15, cx, cy, discR);
      plate.addColorStop(0, "#fff7e6");
      plate.addColorStop(0.75, "#f4ead4");
      plate.addColorStop(1, "#e6d8ba");
      ctx!.beginPath();
      ctx!.arc(cx, cy, discR, 0, Math.PI * 2);
      ctx!.fillStyle = plate;
      ctx!.fill();

      ctx!.save();
      ctx!.translate(cx, cy);
      ctx!.rotate(rot);
      ctx!.beginPath();
      for (let i = 0; i < pathData.length; i += 1) {
        const p = pathData[i];
        const sx = p.x * scale, sy = p.y * scale;
        if (i === 0) { ctx!.moveTo(sx, sy); } else { ctx!.lineTo(sx, sy); }
      }
      ctx!.closePath();
      ctx!.strokeStyle = "rgba(10,79,232,.82)";
      ctx!.lineWidth = Math.max(1.6, scale * 0.022);
      ctx!.lineJoin = "round";
      ctx!.stroke();
      ctx!.restore();

      ctx!.save();
      ctx!.beginPath();
      ctx!.arc(cx, cy, discR, 0, Math.PI * 2);
      ctx!.clip();
      const bandCenter = (sweepProgress * 2 - 0.5) * discR * 2.2;
      ctx!.translate(cx, cy);
      ctx!.rotate(-0.5);
      const glossGrad = ctx!.createLinearGradient(bandCenter - discR * 0.35, 0, bandCenter + discR * 0.35, 0);
      glossGrad.addColorStop(0, "rgba(255,255,255,0)");
      glossGrad.addColorStop(0.5, "rgba(255,255,255,.32)");
      glossGrad.addColorStop(1, "rgba(255,255,255,0)");
      ctx!.fillStyle = glossGrad;
      ctx!.fillRect(bandCenter - discR * 0.4, -discR * 1.5, discR * 0.8, discR * 3);
      ctx!.restore();
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    fit();

    let raf = 0;
    if (reduce) {
      root.classList.remove("is-demo");
      render(0, 0.5);
    } else {
      let startTs: number | null = null;
      const onResize = () => { fit(); };
      function tick(ts: number) {
        if (startTs === null) startTs = ts;
        const elapsed = (ts - startTs) / 1000;
        const rot = elapsed * ROTATE_SPEED;
        const sweepProgress = (elapsed % GLOSS_SWEEP_SECONDS) / GLOSS_SWEEP_SECONDS;
        render(rot, sweepProgress);
        raf = requestAnimationFrame(tick);
      }
      window.addEventListener("resize", onResize);
      raf = requestAnimationFrame(tick);
      return () => {
        cancelAnimationFrame(raf);
        window.removeEventListener("resize", onResize);
      };
    }
    return () => { cancelAnimationFrame(raf); };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.sp8} is-demo`} ref={rootRef} tabIndex={0}>
        <canvas className={styles.sp8__canvas} ref={canvasRef} width={480} height={300} />
        <p className={styles.sp8__caption}>곡선이 다 그려진 뒤 캔버스 전체를 회전 변환으로 천천히 돌려 무늬의 대칭 축을 지나가는 순간마다 겹쳐 보이는 착시가 생기고, 회전 각도 값이 그 리듬을 정한다</p>
      </div>
    </main>
  );
}