03Smoke Whose Thickness Changes With the Emission-Rate Value

<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">Raising the emission-rate value packs more overlapping particles on screen, making the smoke read thicker and more opaque.</p>
  <div class="smk__control">
    <label class="smk__label" for="smkRate">Emission rate</label>
    <input class="smk__range" id="smkRate" type="range" min="2" max="22" value="4" step="1" aria-label="Emission rate">
  </div>
</div>
</main>

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

.smk {
  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-orange;
}

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

.smk__caption {
  position: absolute;
  left: $sp-3;
  top: $sp-3;
  max-width: 70%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

.smk__control {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  gap: $sp-2;
  box-sizing: border-box;
  padding: $sp-2 $sp-3;
  background: rgba(23, 20, 26, .55);
}

.smk__label {
  flex: 0 0 auto;
  font-size: 11px;
  font-weight: 600;
  color: $stage-paper;
  white-space: nowrap;
}

.smk__range {
  flex: 1 1 auto;
  min-width: 0;
  width: 0;
  accent-color: $subject-orange-deep;
}

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

@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: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.smk {
  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: #ff4d1f;
}

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

.smk__caption {
  position: absolute;
  left: 12px;
  top: 12px;
  max-width: 70%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

.smk__control {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  gap: 8px;
  box-sizing: border-box;
  padding: 8px 12px;
  background: rgba(23, 20, 26, 0.55);
}

.smk__label {
  flex: 0 0 auto;
  font-size: 11px;
  font-weight: 600;
  color: #ffffff;
  white-space: nowrap;
}

.smk__range {
  flex: 1 1 auto;
  min-width: 0;
  width: 0;
  accent-color: #c93000;
}

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

(function () {
  // 기법: 초당 발생 수(emissionRate)만큼 입자를 계속 만들어내고, 살아있는 입자마다 옅은
  // 알파로 겹쳐 그린다(source-over). 겹치는 입자 수가 많아질수록 알파가 누적되어 짙고
  // 불투명하게 보이는 게 실제 계산 결과다 — 색을 진하게 바꾸는 게 아니라 개수가 밀도를 만든다.
  var root = document.getElementById('smkRoot');
  var canvas = document.getElementById('smkCanvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;
  var rateInput = document.getElementById('smkRate');

  var CALC_W = 160, CALC_H = 100;
  var SMOKE_EMISSION_RATE = 4;
  var SMOKE_RISE_SPEED_PX = 14;
  var PLUME_LIFE_MS = 2200;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  var NOISE_DIM = 40;
  var noiseRand = seedRand(423031);
  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(423032);
  var particles = [];
  var spawnAcc = 0;
  var emissionRate = SMOKE_EMISSION_RATE;

  rateInput.addEventListener('input', function () {
    root.classList.remove('is-demo');   // 사람이 만졌으니 자동 스윕을 끈다
    emissionRate = parseFloat(rateInput.value);
  });

  function spawn(bornMs) {
    particles.push({
      bx: CALC_W * (0.28 + pRand() * 0.44),
      y: CALC_H - 6,
      born: bornMs,
      wSeed: pRand() * 1000
    });
  }

  function stepSim(dtMs, nowMs) {
    var dtS = dtMs / 1000;
    spawnAcc += dtMs * emissionRate / 1000;
    while (spawnAcc >= 1) { spawn(nowMs); spawnAcc -= 1; }
    var alive = [];
    for (var i = 0; i < particles.length; i += 1) {
      var p = particles[i];
      p.y -= SMOKE_RISE_SPEED_PX * dtS;
      if (nowMs - p.born < PLUME_LIFE_MS) alive.push(p);
    }
    particles = alive;
    if (particles.length > 320) particles = particles.slice(particles.length - 320);
  }

  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 f = Math.max(0, Math.min(1, (nowMs - p.born) / PLUME_LIFE_MS));
      var turb = (valueNoise2D(p.wSeed * 0.03, nowMs * 0.0015) - 0.5) * 2;
      var x = p.bx + turb * 14 * f;
      var r = 8 + f * 20;
      var alpha = Math.sin(f * Math.PI) * 0.22;
      if (alpha <= 0.01) continue;
      var dx = x * sx, dy = p.y * sy, dr = r * ((sx + sy) / 2);
      var g = ctx.createRadialGradient(dx, dy, 0, dx, dy, dr);
      g.addColorStop(0, 'rgba(30,26,20,' + alpha + ')');
      g.addColorStop(1, 'rgba(30,26,20,0)');
      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');

  rateInput.addEventListener('input', function () {
    if (reduce) drawSmoke(elapsed);
  });

  var warmSteps = 140;
  for (var w = 0; w < warmSteps; w += 1) { elapsed += 20; stepSim(20, elapsed); }

  var lastTs = null;
  var demoPhase = 0;
  var DEMO_SWEEP_MS = 2000;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!reduce) {
      elapsed += dt;
      if (root.classList.contains('is-demo')) {
        demoPhase = (demoPhase + dt) % DEMO_SWEEP_MS;
        var t = demoPhase / DEMO_SWEEP_MS;
        var sweep = t < 0.5 ? t * 2 : (1 - t) * 2;
        emissionRate = 3 + sweep * 17;
      }
      stepSim(dt, elapsed);
      drawSmoke(elapsed);
    }
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  drawSmoke(elapsed);
  requestAnimationFrame(tick);
})();

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

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

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

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

    const CALC_W = 160, CALC_H = 100;
    const SMOKE_EMISSION_RATE = 4;
    const SMOKE_RISE_SPEED_PX = 14;
    const PLUME_LIFE_MS = 2200;
    const PARTICLE_CAP = 320;
    const DEMO_SWEEP_MS = 2000;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const NOISE_DIM = 40;
    const noiseRand = seedRand(423030);
    const noiseTable = new Float32Array(NOISE_DIM * NOISE_DIM);
    for (let ni = 0; ni < noiseTable.length; ni += 1) noiseTable[ni] = noiseRand();
    function noiseAt(xi: number, yi: number) {
      const wx = ((xi % NOISE_DIM) + NOISE_DIM) % NOISE_DIM;
      const wy = ((yi % NOISE_DIM) + NOISE_DIM) % NOISE_DIM;
      return noiseTable[wy * NOISE_DIM + wx];
    }
    function smoothstep(t: number) { return t * t * (3 - 2 * t); }
    function valueNoise2D(x: number, y: number) {
      const x0 = Math.floor(x), y0 = Math.floor(y);
      const tx = smoothstep(x - x0), ty = smoothstep(y - y0);
      const v00 = noiseAt(x0, y0), v10 = noiseAt(x0 + 1, y0);
      const v01 = noiseAt(x0, y0 + 1), v11 = noiseAt(x0 + 1, y0 + 1);
      const a = v00 + (v10 - v00) * tx;
      const b = v01 + (v11 - v01) * tx;
      return a + (b - a) * ty;
    }

    const pRand = seedRand(423031);
    let particles: Particle[] = [];
    let spawnAcc = 0;
    let emissionRate = SMOKE_EMISSION_RATE;

    function spawn(bornMs: number) {
      particles.push({
        x: CALC_W * 0.5 + (pRand() - 0.5) * 14,
        y: CALC_H - 6,
        born: bornMs,
        wSeed: pRand() * 1000
      });
    }

    function stepSim(dtMs: number, nowMs: number) {
      const dtS = dtMs / 1000;
      spawnAcc += dtMs * emissionRate / 1000;
      while (spawnAcc >= 1) {
        if (particles.length < PARTICLE_CAP) spawn(nowMs);
        spawnAcc -= 1;
      }
      const alive: Particle[] = [];
      for (let i = 0; i < particles.length; i += 1) {
        const p = particles[i];
        const turb = (valueNoise2D(p.wSeed * 0.03, nowMs * 0.0016) - 0.5) * 2;
        p.x += turb * 6 * dtS;
        p.y -= SMOKE_RISE_SPEED_PX * dtS;
        if (nowMs - p.born < PLUME_LIFE_MS) 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 f = Math.max(0, Math.min(1, (nowMs - p.born) / PLUME_LIFE_MS));
        const r = 6 + f * 14;
        const alpha = Math.sin(f * Math.PI) * 0.22;
        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(50,32,20," + alpha + ")");
        g.addColorStop(1, "rgba(50,32,20,0)");
        ctx!.fillStyle = g;
        ctx!.beginPath();
        ctx!.arc(dx, dy, dr, 0, Math.PI * 2);
        ctx!.fill();
      }
    }

    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");

    let userDriven = false;
    function onRangeInput() {
      userDriven = true;
      emissionRate = Number(range!.value);
      if (reduce) { stepSim(16, elapsed); drawSmoke(elapsed); }
    }
    range.addEventListener("input", onRangeInput);

    const warmSteps = reduce ? 160 : 130;
    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;
        if (!userDriven && root!.classList.contains("is-demo")) {
          const phase = (elapsed % DEMO_SWEEP_MS) / DEMO_SWEEP_MS;
          const tri = phase < 0.5 ? phase * 2 : 2 - phase * 2;
          emissionRate = 3 + tri * 17;
          range!.value = String(Math.round(emissionRate));
        }
        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);
      range.removeEventListener("input", onRangeInput);
    };
  }, []);

  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}>발생량 값을 올리면 한 화면에 겹치는 입자 수가 늘어 연기가 더 짙고 불투명하게 보인다</p>
        <div className={styles.smk__control}>
          <label className={styles.smk__label} htmlFor="smkRate423react">발생량</label>
          <input
            className={styles.smk__range}
            id="smkRate423react"
            ref={rangeRef}
            type="range"
            min={2}
            max={22}
            defaultValue={4}
            aria-label="발생량"
          />
        </div>
      </div>
    </main>
  );
}