03Pointer-Driven Color Ripple

<main class="stage">
<div class="pv is-demo" id="pvRoot">
  <canvas class="pv__canvas" id="pvCanvas" width="480" height="300"></canvas>
  <p class="pv__caption">A background where color ripples spread from the pointer and distort the screen</p>
</div>
</main>

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

.pv {
  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;
}

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

.pv__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 72%;
  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;
}

.pv__step {
  position: absolute;
  right: $sp-3;
  top: $sp-3;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 247, 230, .85);
  color: $subject-ink;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
  pointer-events: none;
}

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

@media (prefers-reduced-motion: reduce) {
  .pv { 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);
}

.pv {
  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);
}

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

.pv__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 72%;
  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;
}

.pv__step {
  position: absolute;
  right: 12px;
  top: 12px;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.85);
  color: #17141a;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
  pointer-events: none;
}

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

(function () {
  // 기법: 대각선 무지개 그라데이션의 샘플 좌표를 포인터에서 퍼지는 사인파동만큼 밀어(distort)
  // 그 밀린 좌표로 색을 계산한다 — 파동이 지나간 자리의 색이 일그러져 보인다.
  var root = document.getElementById('pvRoot');
  var canvas = document.getElementById('pvCanvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  var CALC_W = 160, CALC_H = 100;
  var LOOP_MS = 2000;
  var PLASMA_RIPPLE_SPEED = 0.09;
  var PLASMA_RIPPLE_FREQ = 0.35;
  var PLASMA_RIPPLE_DECAY = 0.014;
  var PLASMA_RIPPLE_AMP = 7;
  var ORBIT_FREQ = Math.PI * 2 / LOOP_MS;

  function hslToRgb(h, s, l) {
    h = ((h % 360) + 360) % 360;
    var c = (1 - Math.abs(2 * l - 1)) * s;
    var x = c * (1 - Math.abs((h / 60) % 2 - 1));
    var m = l - c / 2;
    var r, g, b;
    if (h < 60) { r = c; g = x; b = 0; }
    else if (h < 120) { r = x; g = c; b = 0; }
    else if (h < 180) { r = 0; g = c; b = x; }
    else if (h < 240) { r = 0; g = x; b = c; }
    else if (h < 300) { r = x; g = 0; b = c; }
    else { r = c; g = 0; b = x; }
    return [(r + m) * 255, (g + m) * 255, (b + m) * 255];
  }

  var off = document.createElement('canvas');
  off.width = CALC_W; off.height = CALC_H;
  var octx = off.getContext('2d');
  var offImg = octx.createImageData(CALC_W, CALC_H);
  var offBuf = offImg.data;

  var pointerActive = false;
  var realPointer = { x: CALC_W / 2, y: CALC_H / 2 };
  function virtualPointerOrbit(t) {
    var cx = CALC_W / 2, cy = CALC_H / 2;
    var orbR = Math.min(CALC_W, CALC_H) * 0.4;
    return { x: cx + Math.cos(t * ORBIT_FREQ) * orbR, y: cy + Math.sin(t * ORBIT_FREQ * 1.3) * orbR * 0.7 };
  }

  function renderField(t) {
    var p = pointerActive ? realPointer : (reduce ? { x: -999, y: -999 } : virtualPointerOrbit(t));
    var idx = 0;
    for (var y = 0; y < CALC_H; y += 1) {
      for (var x = 0; x < CALC_W; x += 1) {
        var dx = x - p.x, dy = y - p.y;
        var dist = Math.sqrt(dx * dx + dy * dy) || 0.0001;
        var wave = Math.sin(dist * PLASMA_RIPPLE_FREQ - t * PLASMA_RIPPLE_SPEED);
        var atten = Math.exp(-dist * PLASMA_RIPPLE_DECAY);
        var disp = wave * atten * PLASMA_RIPPLE_AMP;
        var bx = x + (dx / dist) * disp, by = y + (dy / dist) * disp;
        var hue = bx * 1.6 + by * 1.6;
        var light = 0.48 + wave * atten * 0.16;
        var rgb = hslToRgb(hue, 0.64, light);
        offBuf[idx] = rgb[0]; offBuf[idx + 1] = rgb[1]; offBuf[idx + 2] = rgb[2]; offBuf[idx + 3] = 255;
        idx += 4;
      }
    }
  }

  var cw = 480, ch = 300;
  function fit() {
    var r = wrap.getBoundingClientRect();
    cw = Math.max(1, Math.round(r.width));
    ch = Math.max(1, Math.round(r.height));
    canvas.width = cw; canvas.height = ch;
    draw(lastElapsed);
  }

  var lastElapsed = 0;
  function draw(elapsed) {
    lastElapsed = elapsed;
    renderField(elapsed);
    octx.putImageData(offImg, 0, 0);
    ctx.clearRect(0, 0, cw, ch);
    ctx.drawImage(off, 0, 0, CALC_W, CALC_H, 0, 0, cw, ch);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var playing = !reduce;
  var elapsed = reduce ? 0 : 0;
  if (reduce) { root.classList.remove('is-demo'); }

  function calcFromEvent(e) {
    var r = wrap.getBoundingClientRect();
    var t0 = (e.touches && e.touches[0]) ? e.touches[0] : e;
    var relX = (t0.clientX - r.left) / r.width * cw;
    var relY = (t0.clientY - r.top) / r.height * ch;
    realPointer.x = relX * (CALC_W / cw);
    realPointer.y = relY * (CALC_H / ch);
  }
  wrap.addEventListener('pointermove', function (e) {
    pointerActive = true;
    calcFromEvent(e);
    draw(lastElapsed);
  });
  wrap.addEventListener('pointerleave', function () {
    pointerActive = false;
    draw(lastElapsed);
  });

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = ts - lastTs;
    lastTs = ts;
    if (playing) {
      elapsed += dt;
      if (elapsed >= LOOP_MS) elapsed -= LOOP_MS;
    }
    draw(elapsed);
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  draw(elapsed);
  requestAnimationFrame(tick);
})();

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

export default function PlasmaPointerRippleDistort() {
  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_W = 160, CALC_H = 100;
    const LOOP_MS = 2000;
    const PLASMA_RIPPLE_SPEED = 0.09;
    const PLASMA_RIPPLE_FREQ = 0.35;
    const PLASMA_RIPPLE_DECAY = 0.014;
    const PLASMA_RIPPLE_AMP = 7;
    const ORBIT_FREQ = (Math.PI * 2) / LOOP_MS;

    function hslToRgb(h: number, s: number, l: number): [number, number, number] {
      h = ((h % 360) + 360) % 360;
      const c = (1 - Math.abs(2 * l - 1)) * s;
      const x = c * (1 - Math.abs(((h / 60) % 2) - 1));
      const m = l - c / 2;
      let r = 0, g = 0, b = 0;
      if (h < 60) { r = c; g = x; b = 0; }
      else if (h < 120) { r = x; g = c; b = 0; }
      else if (h < 180) { r = 0; g = c; b = x; }
      else if (h < 240) { r = 0; g = x; b = c; }
      else if (h < 300) { r = x; g = 0; b = c; }
      else { r = c; g = 0; b = x; }
      return [(r + m) * 255, (g + m) * 255, (b + m) * 255];
    }

    type Vec = { x: number; y: number };
    let pointerActive = false;
    const realPointer: Vec = { x: CALC_W / 2, y: CALC_H / 2 };

    function virtualPointerOrbit(t: number): Vec {
      const cx = CALC_W / 2, cy = CALC_H / 2;
      const orbR = Math.min(CALC_W, CALC_H) * 0.38;
      return { x: cx + Math.cos(t * ORBIT_FREQ) * orbR, y: cy + Math.sin(t * ORBIT_FREQ * 1.4) * orbR * 0.7 };
    }

    const off = document.createElement("canvas");
    off.width = CALC_W; off.height = CALC_H;
    const octx = off.getContext("2d") as CanvasRenderingContext2D;
    const offImg = octx.createImageData(CALC_W, CALC_H);
    const offBuf = offImg.data;

    let reduce = false;
    function renderField(t: number) {
      const p = pointerActive ? realPointer : (reduce ? { x: -999, y: -999 } : virtualPointerOrbit(t));
      let idx = 0;
      for (let y = 0; y < CALC_H; y += 1) {
        for (let x = 0; x < CALC_W; x += 1) {
          const dx = x - p.x, dy = y - p.y;
          const dist = Math.sqrt(dx * dx + dy * dy);
          const wave = Math.sin(dist * PLASMA_RIPPLE_FREQ - t * PLASMA_RIPPLE_SPEED);
          const atten = Math.exp(-dist * PLASMA_RIPPLE_DECAY);
          const disp = wave * atten * PLASMA_RIPPLE_AMP;
          const bx = x + (dx / (dist || 1)) * disp;
          const by = y + (dy / (dist || 1)) * disp;
          const hue = bx * 1.6 + by * 1.6 + t * 0.03;
          const rgb = hslToRgb(hue, 0.7, 0.5 + wave * atten * 0.12);
          offBuf[idx] = rgb[0]; offBuf[idx + 1] = rgb[1]; offBuf[idx + 2] = rgb[2]; offBuf[idx + 3] = 255;
          idx += 4;
        }
      }
    }

    let cw = 480, ch = 300;
    function fit() {
      const r = wrap.getBoundingClientRect();
      cw = Math.max(1, Math.round(r.width));
      ch = Math.max(1, Math.round(r.height));
      canvas!.width = cw; canvas!.height = ch;
      draw(lastElapsed);
    }

    let lastElapsed = 0;
    function draw(elapsed: number) {
      lastElapsed = elapsed;
      renderField(elapsed);
      octx.putImageData(offImg, 0, 0);
      ctx!.imageSmoothingEnabled = false;
      ctx!.clearRect(0, 0, cw, ch);
      ctx!.drawImage(off, 0, 0, CALC_W, CALC_H, 0, 0, cw, ch);
    }

    reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let playing = !reduce;
    let elapsed = reduce ? LOOP_MS * 0.5 : 0;
    if (reduce) { root.classList.remove("is-demo"); }

    function calcFromEvent(e: PointerEvent) {
      const r = wrap.getBoundingClientRect();
      const relX = ((e.clientX - r.left) / r.width) * cw;
      const relY = ((e.clientY - r.top) / r.height) * ch;
      realPointer.x = relX * (CALC_W / cw);
      realPointer.y = relY * (CALC_H / ch);
    }
    function onPointerMove(e: PointerEvent) {
      pointerActive = true;
      calcFromEvent(e);
      draw(lastElapsed);
    }
    function onPointerLeave() {
      pointerActive = false;
      draw(lastElapsed);
    }
    wrap.addEventListener("pointermove", onPointerMove);
    wrap.addEventListener("pointerleave", onPointerLeave);

    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = ts - lastTs;
      lastTs = ts;
      if (playing) {
        elapsed += dt;
        if (elapsed >= LOOP_MS) elapsed -= LOOP_MS;
      }
      draw(elapsed);
      raf = requestAnimationFrame(tick);
    }
    fit();
    window.addEventListener("resize", fit);
    draw(elapsed);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("resize", fit);
      wrap.removeEventListener("pointermove", onPointerMove);
      wrap.removeEventListener("pointerleave", onPointerLeave);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.pv} is-demo`} ref={rootRef}>
        <canvas className={styles.pv__canvas} ref={canvasRef} width={480} height={300} />
        <p className={styles.pv__caption}>포인터를 중심으로 색 파동이 퍼지며 화면을 일그러뜨리는 배경</p>
      </div>
    </main>
  );
}