04Smoke That Fades and Dissolves the Farther It Drifts From Its Source

<main class="stage">
<div class="smk is-demo" id="smkRoot">
  <canvas class="smk__canvas" id="smkCanvas" width="480" height="300"></canvas>
  <p class="smk__caption">Opacity drops in step with distance from the source, and past a set distance the particle disappears completely.</p>
</div>
</main>

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

.smk {
  box-sizing: border-box;
  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;
  border: 1px solid rgba(23, 20, 26, .08);
}

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

.smk__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(23, 20, 26, .78);
  color: $stage-paper;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

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

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

.smk {
  box-sizing: border-box;
  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;
  border: 1px solid rgba(23, 20, 26, 0.08);
}

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

.smk__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 78%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #ffffff;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

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

(function () {
  // 기법: 발원지(원점) 좌표를 저장해두고, 매 프레임 입자와 원점 사이의 유클리드 거리를 계산한다.
  // 거리를 SMOKE_DISSOLVE_MS(=이동 속도 x 시간으로 환산한 소멸 거리)로 나눈 비율만큼 알파를
  // 선형으로 깎는다 — 나이가 아니라 "거리"가 직접 불투명도를 정한다. 거리가 소멸 거리를
  // 넘어서면 배열에서 제거한다.
  var root = document.getElementById('smkRoot');
  var canvas = document.getElementById('smkCanvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  var CALC_W = 160, CALC_H = 100;
  var SMOKE_DISSOLVE_MS = 900;
  var DRIFT_SPEED_PX_S = 30;
  var DISSOLVE_DISTANCE = (SMOKE_DISSOLVE_MS / 1000) * DRIFT_SPEED_PX_S;
  var SPAWN_PER_S = 30;
  var SOURCE_X = CALC_W * 0.5, SOURCE_Y = CALC_H * 0.62;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  var NOISE_DIM = 40;
  var noiseRand = seedRand(423041);
  var noiseTable = new Float32Array(NOISE_DIM * NOISE_DIM);
  for (var ni = 0; ni < noiseTable.length; ni += 1) noiseTable[ni] = noiseRand();
  function noiseAt(xi, yi) {
    var wx = ((xi % NOISE_DIM) + NOISE_DIM) % NOISE_DIM;
    var wy = ((yi % NOISE_DIM) + NOISE_DIM) % NOISE_DIM;
    return noiseTable[wy * NOISE_DIM + wx];
  }
  function smoothstep(t) { return t * t * (3 - 2 * t); }
  function valueNoise2D(x, y) {
    var x0 = Math.floor(x), y0 = Math.floor(y);
    var tx = smoothstep(x - x0), ty = smoothstep(y - y0);
    var v00 = noiseAt(x0, y0), v10 = noiseAt(x0 + 1, y0);
    var v01 = noiseAt(x0, y0 + 1), v11 = noiseAt(x0 + 1, y0 + 1);
    var a = v00 + (v10 - v00) * tx;
    var b = v01 + (v11 - v01) * tx;
    return a + (b - a) * ty;
  }

  var pRand = seedRand(423042);
  var particles = [];
  var spawnAcc = 0;

  function spawn() {
    var ang = -Math.PI / 2 + (pRand() - 0.5) * Math.PI * 0.9;
    particles.push({
      x: SOURCE_X, y: SOURCE_Y,
      vx: Math.cos(ang) * DRIFT_SPEED_PX_S,
      vy: Math.sin(ang) * DRIFT_SPEED_PX_S,
      wSeed: pRand() * 1000
    });
  }

  function stepSim(dtMs) {
    var dtS = dtMs / 1000;
    spawnAcc += dtMs * SPAWN_PER_S / 1000;
    while (spawnAcc >= 1) { spawn(); spawnAcc -= 1; }
    var alive = [];
    for (var i = 0; i < particles.length; i += 1) {
      var p = particles[i];
      p.x += p.vx * dtS;
      p.y += p.vy * dtS;
      var dist = Math.hypot(p.x - SOURCE_X, p.y - SOURCE_Y);
      if (dist < DISSOLVE_DISTANCE) alive.push(p);
    }
    particles = alive;
  }

  function drawSmoke(nowMs) {
    var sx = cw / CALC_W, sy = ch / CALC_H;
    ctx.clearRect(0, 0, cw, ch);
    for (var i = 0; i < particles.length; i += 1) {
      var p = particles[i];
      var dist = Math.hypot(p.x - SOURCE_X, p.y - SOURCE_Y);
      var f = Math.max(0, 1 - dist / DISSOLVE_DISTANCE);
      var turb = (valueNoise2D(p.wSeed * 0.04, nowMs * 0.0016) - 0.5) * 6;
      var r = 6 + (1 - f) * 24;
      var alpha = f * 0.6;
      if (alpha <= 0.01) continue;
      var dx = (p.x + turb) * sx, dy = p.y * sy, dr = r * ((sx + sy) / 2);
      var g = ctx.createRadialGradient(dx, dy, 0, dx, dy, dr);
      g.addColorStop(0, 'rgba(35,32,40,' + alpha + ')');
      g.addColorStop(1, 'rgba(35,32,40,0)');
      ctx.fillStyle = g;
      ctx.beginPath();
      ctx.arc(dx, dy, dr, 0, Math.PI * 2);
      ctx.fill();
    }
  }

  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;
    drawSmoke(elapsed);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var elapsed = 0;
  if (reduce) root.classList.remove('is-demo');
  var warmSteps = 60;
  for (var w = 0; w < warmSteps; w += 1) { elapsed += 20; stepSim(20); }

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!reduce) {
      elapsed += dt;
      stepSim(dt);
      drawSmoke(elapsed);
    }
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  drawSmoke(elapsed);
  requestAnimationFrame(tick);
})();

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

type Particle = { x: number; y: number; ang: number; born: number };

export default function SmokeEffectDistanceFadeDissolve() {
  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 SMOKE_DISSOLVE_MS = 900;
    const DRIFT_SPEED_PX_S = 30;
    const DISSOLVE_DISTANCE = (SMOKE_DISSOLVE_MS / 1000) * DRIFT_SPEED_PX_S;
    const SOURCE_X = CALC_W * 0.5, SOURCE_Y = CALC_H * 0.55;
    const SPAWN_PER_S = 30;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const pRand = seedRand(423041);
    let particles: Particle[] = [];
    let spawnAcc = 0;

    function spawn(bornMs: number) {
      particles.push({ x: SOURCE_X, y: SOURCE_Y, ang: pRand() * Math.PI * 2, born: bornMs });
    }

    function stepSim(dtMs: number, nowMs: number) {
      const dtS = dtMs / 1000;
      spawnAcc += dtMs * SPAWN_PER_S / 1000;
      while (spawnAcc >= 1) { spawn(nowMs); spawnAcc -= 1; }
      const alive: Particle[] = [];
      for (let i = 0; i < particles.length; i += 1) {
        const p = particles[i];
        p.x += Math.cos(p.ang) * DRIFT_SPEED_PX_S * dtS;
        p.y += Math.sin(p.ang) * DRIFT_SPEED_PX_S * dtS - DRIFT_SPEED_PX_S * 0.2 * dtS;
        const dist = Math.hypot(p.x - SOURCE_X, p.y - SOURCE_Y);
        if (dist < DISSOLVE_DISTANCE && nowMs - p.born < 4000) alive.push(p);
      }
      particles = alive;
    }

    let cw = 480, ch = 300;
    function drawSmoke(nowMs: number) {
      const sx = cw / CALC_W, sy = ch / CALC_H;
      ctx!.clearRect(0, 0, cw, ch);
      for (let i = 0; i < particles.length; i += 1) {
        const p = particles[i];
        const dist = Math.hypot(p.x - SOURCE_X, p.y - SOURCE_Y);
        const f = Math.max(0, 1 - dist / DISSOLVE_DISTANCE);
        const r = 6 + (1 - f) * 24;
        const alpha = f * 0.6;
        if (alpha <= 0.01) continue;
        const dx = p.x * sx, dy = p.y * sy, dr = r * ((sx + sy) / 2);
        const g = ctx!.createRadialGradient(dx, dy, 0, dx, dy, dr);
        g.addColorStop(0, "rgba(35,32,40," + alpha + ")");
        g.addColorStop(1, "rgba(35,32,40,0)");
        ctx!.fillStyle = g;
        ctx!.beginPath();
        ctx!.arc(dx, dy, dr, 0, Math.PI * 2);
        ctx!.fill();
      }
      void nowMs;
    }

    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;
      drawSmoke(elapsed);
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let elapsed = 0;
    if (reduce) root.classList.remove("is-demo");
    const warmSteps = reduce ? 140 : 100;
    for (let w = 0; w < warmSteps; w += 1) { elapsed += 20; stepSim(20, elapsed); }

    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min(ts - lastTs, 48);
      lastTs = ts;
      if (!reduce) {
        elapsed += dt;
        stepSim(dt, elapsed);
        drawSmoke(elapsed);
      }
      raf = requestAnimationFrame(tick);
    }
    fit();
    window.addEventListener("resize", fit);
    drawSmoke(elapsed);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("resize", fit);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.smk} is-demo`} ref={rootRef}>
        <canvas className={styles.smk__canvas} ref={canvasRef} width={480} height={300} />
        <p className={styles.smk__caption}>발원지에서 멀어진 거리만큼 입자의 불투명도가 줄어들다가 일정 거리를 넘으면 완전히 사라진다</p>
      </div>
    </main>
  );
}