04Tails Drawn From Position History and a Glow That Brightens Where They Overlap
Each grain keeps its last N positions, joins them with a line fading toward the old end, and additive blending lets overlaps bloom to white.
Best forNight hero backgrounds and game victory screens
TRAIL_LENGLOW_BLURFADE_ALPHAHEAD_R
<main class="stage">
<div class="sc is-demo" id="scRoot">
<canvas class="sc__canvas" id="scCanvas" width="480" height="300" tabindex="0" aria-label="Tails Drawn From Position History and a Glow That Brightens Where They Overlap"></canvas>
<p class="sc__status" id="scStatus" aria-live="polite">Trail history stacked additively — overlaps bloom white</p>
<button class="sc__btn" id="scBtn" type="button">Pause</button>
<p class="sc__caption">Tails Drawn From Position History and a Glow That Brightens Where They Overlap</p>
</div>
</main>@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);
.sc {
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: $subject-ink;
}
.sc__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: manipulation;
}
.sc__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, .85);
outline-offset: -6px;
}
.sc__status {
position: absolute;
left: $sp-3;
top: $sp-3;
max-width: 62%;
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: 11px;
line-height: 1.4;
pointer-events: none;
}
.sc__btn {
position: absolute;
right: $sp-3;
bottom: $sp-3;
margin: 0;
padding: $sp-1 $sp-3;
border: 0;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.sc__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.sc__caption {
position: absolute;
left: $sp-3;
bottom: $sp-3;
max-width: 68%;
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;
}
@media (max-width: 340px) {
.sc__caption, .sc__btn { font-size: 10px; padding: $sp-1 $sp-2; }
.sc__status { font-size: 10px; }
}
@media (prefers-reduced-motion: reduce) {
.sc { cursor: default; }
}html, body {
margin: 0;
overflow: hidden;
}
.stage {
box-sizing: border-box;
min-height: 100vh;
display: grid;
place-items: center;
margin: 0;
background: #17141a;
font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
padding: clamp(8px, 4vw, 24px);
}
.sc {
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: #17141a;
}
.sc__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: manipulation;
}
.sc__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, 0.85);
outline-offset: -6px;
}
.sc__status {
position: absolute;
left: 12px;
top: 12px;
max-width: 62%;
margin: 0;
padding: 4px 12px;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font-weight: 500;
font-size: 11px;
line-height: 1.4;
pointer-events: none;
}
.sc__btn {
position: absolute;
right: 12px;
bottom: 12px;
margin: 0;
padding: 4px 12px;
border: 0;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.sc__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.sc__caption {
position: absolute;
left: 12px;
bottom: 12px;
max-width: 68%;
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;
}
@media (max-width: 340px) {
.sc__caption, .sc__btn {
font-size: 10px;
padding: 4px 8px;
}
.sc__status {
font-size: 10px;
}
}
@media (prefers-reduced-motion: reduce) {
.sc {
cursor: default;
}
}(function () {
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const REDUCE_STEP_MS = 900;
const KEY_STEP = 14;
const IDLE_TICKS = 150;
const BTN_PAUSE = 'Pause';
const BTN_PLAY = 'Play';
const BTN_NEXT = 'Next scene';
// 파스텔 알갱이 팔레트와 밤하늘 두 끝 색
const PINK = [255, 170, 196];
const MINT = [150, 226, 196];
const LILAC = [196, 176, 255];
const SKY_BLUE = [150, 214, 255];
const BUTTER = [255, 230, 150];
const CREAM = [255, 247, 230];
const PALETTE = [PINK, MINT, LILAC, SKY_BLUE, BUTTER];
const SKY_TOP = [18, 16, 32];
const SKY_BOT = [46, 40, 76];
function clamp(v, lo, hi) { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a, b, k) { return a + (b - a) * k; }
function smooth(x) { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed) {
let s = seed >>> 0;
return function () {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 하나와 시드로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash1(i, seed) {
let h = (Math.imul(i | 0, 374761393) + Math.imul(seed | 0, 668265263)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
function hash2(x, y, seed) {
return hash1((Math.imul(x | 0, 73856093) ^ Math.imul(y | 0, 19349663)) | 0, seed);
}
// 1차원 값 노이즈 — 정수점 해시를 smooth 로 이어 붙인다
function noise1(x, seed) {
const xi = Math.floor(x);
return lerp(hash1(xi, seed), hash1(xi + 1, seed), smooth(x - xi));
}
// 2차원 값 노이즈
function vnoise(x, y, seed) {
const xi = Math.floor(x);
const yi = Math.floor(y);
const fx = smooth(x - xi);
const fy = smooth(y - yi);
const a = lerp(hash2(xi, yi, seed), hash2(xi + 1, yi, seed), fx);
const b = lerp(hash2(xi, yi + 1, seed), hash2(xi + 1, yi + 1, seed), fx);
return lerp(a, b, fy);
}
function rgba(c, a) {
return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
}
function mixRGB(a, b, k) {
return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)];
}
// 밤하늘 바탕 — 위가 어둡고 아래가 보랏빛
function drawSky(ctx, height) {
const g = ctx.createLinearGradient(0, 0, 0, height);
g.addColorStop(0, rgba(SKY_TOP, 1));
g.addColorStop(1, rgba(SKY_BOT, 1));
ctx.fillStyle = g;
ctx.fillRect(0, 0, W, height);
}
function start(root, canvas, statusEl, btnEl, make) {
const ctx0 = canvas.getContext('2d');
if (!ctx0) {
return function () { return; };
}
const ctx = ctx0;
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const inp = { x: W / 2, y: H / 2, idle: 99999, vx: 0, vy: 0, dpr: 1 };
let lastPx = -1;
let lastPy = -1;
// 화면 배율이 바뀌어도 캔버스 픽셀 수를 다시 맞춘다
function fit() {
const dpr = Math.min(window.devicePixelRatio || 1, 2);
inp.dpr = dpr;
canvas.width = Math.round(W * dpr);
canvas.height = Math.round(H * dpr);
ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
}
fit();
const scene = make(inp, reduce);
let paused = false;
let rafId = 0;
let lastTs = -1;
let accMs = 0;
let lastLabel = '';
const cleaners = [];
function listen(target, type, fn) {
target.addEventListener(type, fn);
cleaners.push(function () { target.removeEventListener(type, fn); });
}
function show() {
ctx.setTransform(inp.dpr, 0, 0, inp.dpr, 0, 0);
scene.draw(ctx);
const t = scene.label();
if (t !== lastLabel) {
lastLabel = t;
statusEl.textContent = t;
}
}
function tickOnce() {
inp.idle += 1;
inp.vx *= 0.9;
inp.vy *= 0.9;
scene.step();
}
function advance(ms) {
const n = Math.round(ms / FIXED_DT);
for (let i = 0; i < n; i += 1) {
tickOnce();
}
}
function refresh() {
if (reduce) {
advance(FIXED_DT * 6);
show();
}
}
function toLocal(e) {
const r = canvas.getBoundingClientRect();
const nx = clamp((e.clientX - r.left) * W / r.width, 0, W);
const ny = clamp((e.clientY - r.top) * H / r.height, 0, H);
if (lastPx >= 0) {
inp.vx = lerp(inp.vx, nx - lastPx, 0.5);
inp.vy = lerp(inp.vy, ny - lastPy, 0.5);
}
lastPx = nx;
lastPy = ny;
inp.x = nx;
inp.y = ny;
inp.idle = 0;
}
function tick(ts) {
if (lastTs < 0) {
lastTs = ts;
}
const frameDt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused) {
accMs += frameDt;
while (accMs >= FIXED_DT) {
tickOnce();
accMs -= FIXED_DT;
}
show();
}
rafId = requestAnimationFrame(tick);
}
btnEl.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
if (reduce) {
root.classList.remove('is-demo');
}
show();
listen(btnEl, 'click', function () {
if (reduce) {
advance(REDUCE_STEP_MS);
show();
return;
}
paused = !paused;
if (paused) {
root.classList.remove('is-demo');
}
else {
root.classList.add('is-demo');
}
btnEl.textContent = paused ? BTN_PLAY : BTN_PAUSE;
});
listen(canvas, 'pointermove', function (e) {
toLocal(e);
refresh();
});
listen(canvas, 'pointerdown', function (e) {
lastPx = -1;
toLocal(e);
scene.tap();
refresh();
});
listen(canvas, 'keydown', function (e) {
const k = e.key;
let dx = 0;
let dy = 0;
if (k === 'Enter' || k === ' ') {
e.preventDefault();
scene.tap();
refresh();
return;
}
if (k === 'ArrowLeft') {
dx = -KEY_STEP;
}
else if (k === 'ArrowRight') {
dx = KEY_STEP;
}
else if (k === 'ArrowUp') {
dy = -KEY_STEP;
}
else if (k === 'ArrowDown') {
dy = KEY_STEP;
}
else {
return;
}
e.preventDefault();
inp.x = clamp(inp.x + dx, 0, W);
inp.y = clamp(inp.y + dy, 0, H);
inp.vx = dx * 0.5;
inp.vy = dy * 0.5;
inp.idle = 0;
refresh();
});
listen(window, 'resize', function () {
fit();
show();
});
if (!reduce) {
rafId = requestAnimationFrame(tick);
}
return function () {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) {
cleaners[i]();
}
};
}
const TRAIL_LEN = 16;
const GLOW_BLUR = 9;
const FADE_ALPHA = 0.86;
const HEAD_R = 2.1;
const BURST_GAP = 44;
const SPARK_N = 56;
const SPARK_DRAG = 0.972;
const SPARK_GRAVITY = 0.045;
const PREWARM_STEPS = 38;
const TXT_AUTO = 'Trail history stacked additively — overlaps bloom white';
const TXT_TAP = 'A glow bursts where you press';
// 위치 이력 한 줄에서 i 번째 점의 알파 — 머리에서 멀수록 FADE_ALPHA 를 거듭 곱한다
function trailAlpha(back) {
return Math.pow(FADE_ALPHA, back);
}
function makeScene(inp, reduce) {
const rng = lcg(4004);
let sparks = [];
let gap = 2;
let colorIdx = 0;
const glows = [];
function glowFor(idx) {
if (glows[idx]) {
return glows[idx];
}
const size = GLOW_BLUR * 4;
const cv = document.createElement('canvas');
cv.width = size;
cv.height = size;
const c = cv.getContext('2d');
if (c) {
const g = c.createRadialGradient(size / 2, size / 2, 0, size / 2, size / 2, size / 2);
g.addColorStop(0, rgba(CREAM, 0.9));
g.addColorStop(0.25, rgba(PALETTE[idx], 0.45));
g.addColorStop(1, rgba(PALETTE[idx], 0));
c.fillStyle = g;
c.fillRect(0, 0, size, size);
}
glows[idx] = cv;
return cv;
}
function burst(x, y) {
const hue = colorIdx % PALETTE.length;
colorIdx += 1;
for (let i = 0; i < SPARK_N; i += 1) {
const a = rng() * PI2;
const sp = 2.2 + rng() * 2.4;
sparks.push({ x: x, y: y, vx: Math.cos(a) * sp, vy: Math.sin(a) * sp, age: 0, life: 70 + rng() * 26, hist: [], hue: i % 4 === 0 ? (hue + 1) % PALETTE.length : hue });
}
if (sparks.length > 330) {
sparks.splice(0, sparks.length - 330);
}
}
const scene = {
step() {
gap -= 1;
if (gap <= 0) {
burst(90 + rng() * 300, 80 + rng() * 70);
gap = BURST_GAP;
}
const alive = [];
for (let i = 0; i < sparks.length; i += 1) {
const s = sparks[i];
s.age += 1;
s.hist.push(s.x, s.y);
if (s.hist.length > TRAIL_LEN * 2) {
s.hist.splice(0, 2);
}
s.vx *= SPARK_DRAG;
s.vy = s.vy * SPARK_DRAG + SPARK_GRAVITY;
s.x += s.vx;
s.y += s.vy;
if (s.age < s.life) {
alive.push(s);
}
}
sparks = alive;
},
draw(ctx) {
drawSky(ctx, H);
// 이 항목의 핵심 — 합성 방식을 가산으로 바꾸면 겹친 곳의 색이 더해져 하얗게 번진다
ctx.globalCompositeOperation = 'lighter';
ctx.lineCap = 'round';
for (let i = 0; i < sparks.length; i += 1) {
const s = sparks[i];
const life = Math.pow(1 - s.age / s.life, 0.7);
const n = s.hist.length / 2;
for (let k = 1; k < n; k += 1) {
const a = trailAlpha(n - k) * life;
ctx.strokeStyle = rgba(PALETTE[s.hue], a * 0.85);
ctx.lineWidth = lerp(0.6, HEAD_R * 1.3, k / n);
ctx.beginPath();
ctx.moveTo(s.hist[(k - 1) * 2], s.hist[(k - 1) * 2 + 1]);
ctx.lineTo(s.hist[k * 2], s.hist[k * 2 + 1]);
ctx.stroke();
}
const r = GLOW_BLUR * (0.6 + 0.4 * life);
ctx.globalAlpha = life * (reduce ? 0.6 : 0.85);
ctx.drawImage(glowFor(s.hue), s.x - r, s.y - r, r * 2, r * 2);
ctx.globalAlpha = 1;
ctx.fillStyle = rgba(CREAM, life);
ctx.beginPath();
ctx.arc(s.x, s.y, HEAD_R * (0.5 + 0.5 * life), 0, PI2);
ctx.fill();
}
ctx.globalCompositeOperation = 'source-over';
},
label() {
return inp.idle < IDLE_TICKS ? TXT_TAP : TXT_AUTO;
},
tap() {
burst(inp.x, inp.y);
}
};
for (let i = 0; i < PREWARM_STEPS; i += 1) {
scene.step();
}
return scene;
}
start(document.getElementById('scRoot'), document.getElementById('scCanvas'), document.getElementById('scStatus'), document.getElementById('scBtn'), makeScene);
})();import { useEffect, useRef } from "react";
import styles from "./FwAdditiveTrailHistoryGlow.module.scss";
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const REDUCE_STEP_MS = 900;
const KEY_STEP = 14;
const IDLE_TICKS = 150;
const BTN_PAUSE = '멈춤';
const BTN_PLAY = '재생';
const BTN_NEXT = '다음 장면';
type RGB = [number, number, number];
interface Input { x: number; y: number; idle: number; vx: number; vy: number; dpr: number; }
interface Scene {
step(): void;
draw(ctx: CanvasRenderingContext2D): void;
label(): string;
tap(): void;
}
type Maker = (inp: Input, reduce: boolean) => Scene;
// 파스텔 알갱이 팔레트와 밤하늘 두 끝 색
const PINK: RGB = [255, 170, 196];
const MINT: RGB = [150, 226, 196];
const LILAC: RGB = [196, 176, 255];
const SKY_BLUE: RGB = [150, 214, 255];
const BUTTER: RGB = [255, 230, 150];
const CREAM: RGB = [255, 247, 230];
const PALETTE: RGB[] = [PINK, MINT, LILAC, SKY_BLUE, BUTTER];
const SKY_TOP: RGB = [18, 16, 32];
const SKY_BOT: RGB = [46, 40, 76];
function clamp(v: number, lo: number, hi: number): number { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a: number, b: number, k: number): number { return a + (b - a) * k; }
function smooth(x: number): number { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed: number): () => number {
let s = seed >>> 0;
return function (): number {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 하나와 시드로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash1(i: number, seed: number): number {
let h = (Math.imul(i | 0, 374761393) + Math.imul(seed | 0, 668265263)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
function hash2(x: number, y: number, seed: number): number {
return hash1((Math.imul(x | 0, 73856093) ^ Math.imul(y | 0, 19349663)) | 0, seed);
}
// 1차원 값 노이즈 — 정수점 해시를 smooth 로 이어 붙인다
function noise1(x: number, seed: number): number {
const xi = Math.floor(x);
return lerp(hash1(xi, seed), hash1(xi + 1, seed), smooth(x - xi));
}
// 2차원 값 노이즈
function vnoise(x: number, y: number, seed: number): number {
const xi = Math.floor(x);
const yi = Math.floor(y);
const fx = smooth(x - xi);
const fy = smooth(y - yi);
const a = lerp(hash2(xi, yi, seed), hash2(xi + 1, yi, seed), fx);
const b = lerp(hash2(xi, yi + 1, seed), hash2(xi + 1, yi + 1, seed), fx);
return lerp(a, b, fy);
}
function rgba(c: RGB, a: number): string {
return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
}
function mixRGB(a: RGB, b: RGB, k: number): RGB {
return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)];
}
// 밤하늘 바탕 — 위가 어둡고 아래가 보랏빛
function drawSky(ctx: CanvasRenderingContext2D, height: number): void {
const g = ctx.createLinearGradient(0, 0, 0, height);
g.addColorStop(0, rgba(SKY_TOP, 1));
g.addColorStop(1, rgba(SKY_BOT, 1));
ctx.fillStyle = g;
ctx.fillRect(0, 0, W, height);
}
function start(root: HTMLElement, canvas: HTMLCanvasElement, statusEl: HTMLElement, btnEl: HTMLElement, make: Maker): () => void {
const ctx0 = canvas.getContext('2d');
if (!ctx0) {
return function (): void { return; };
}
const ctx: CanvasRenderingContext2D = ctx0;
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const inp: Input = { x: W / 2, y: H / 2, idle: 99999, vx: 0, vy: 0, dpr: 1 };
let lastPx = -1;
let lastPy = -1;
// 화면 배율이 바뀌어도 캔버스 픽셀 수를 다시 맞춘다
function fit(): void {
const dpr = Math.min(window.devicePixelRatio || 1, 2);
inp.dpr = dpr;
canvas.width = Math.round(W * dpr);
canvas.height = Math.round(H * dpr);
ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
}
fit();
const scene = make(inp, reduce);
let paused = false;
let rafId = 0;
let lastTs = -1;
let accMs = 0;
let lastLabel = '';
const cleaners: Array<() => void> = [];
function listen(target: EventTarget, type: string, fn: (e: any) => void): void {
target.addEventListener(type, fn);
cleaners.push(function (): void { target.removeEventListener(type, fn); });
}
function show(): void {
ctx.setTransform(inp.dpr, 0, 0, inp.dpr, 0, 0);
scene.draw(ctx);
const t = scene.label();
if (t !== lastLabel) {
lastLabel = t;
statusEl.textContent = t;
}
}
function tickOnce(): void {
inp.idle += 1;
inp.vx *= 0.9;
inp.vy *= 0.9;
scene.step();
}
function advance(ms: number): void {
const n = Math.round(ms / FIXED_DT);
for (let i = 0; i < n; i += 1) {
tickOnce();
}
}
function refresh(): void {
if (reduce) {
advance(FIXED_DT * 6);
show();
}
}
function toLocal(e: PointerEvent): void {
const r = canvas.getBoundingClientRect();
const nx = clamp((e.clientX - r.left) * W / r.width, 0, W);
const ny = clamp((e.clientY - r.top) * H / r.height, 0, H);
if (lastPx >= 0) {
inp.vx = lerp(inp.vx, nx - lastPx, 0.5);
inp.vy = lerp(inp.vy, ny - lastPy, 0.5);
}
lastPx = nx;
lastPy = ny;
inp.x = nx;
inp.y = ny;
inp.idle = 0;
}
function tick(ts: number): void {
if (lastTs < 0) {
lastTs = ts;
}
const frameDt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused) {
accMs += frameDt;
while (accMs >= FIXED_DT) {
tickOnce();
accMs -= FIXED_DT;
}
show();
}
rafId = requestAnimationFrame(tick);
}
btnEl.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
if (reduce) {
root.classList.remove('is-demo');
}
show();
listen(btnEl, 'click', function (): void {
if (reduce) {
advance(REDUCE_STEP_MS);
show();
return;
}
paused = !paused;
if (paused) {
root.classList.remove('is-demo');
}
else {
root.classList.add('is-demo');
}
btnEl.textContent = paused ? BTN_PLAY : BTN_PAUSE;
});
listen(canvas, 'pointermove', function (e: PointerEvent): void {
toLocal(e);
refresh();
});
listen(canvas, 'pointerdown', function (e: PointerEvent): void {
lastPx = -1;
toLocal(e);
scene.tap();
refresh();
});
listen(canvas, 'keydown', function (e: KeyboardEvent): void {
const k = e.key;
let dx = 0;
let dy = 0;
if (k === 'Enter' || k === ' ') {
e.preventDefault();
scene.tap();
refresh();
return;
}
if (k === 'ArrowLeft') {
dx = -KEY_STEP;
}
else if (k === 'ArrowRight') {
dx = KEY_STEP;
}
else if (k === 'ArrowUp') {
dy = -KEY_STEP;
}
else if (k === 'ArrowDown') {
dy = KEY_STEP;
}
else {
return;
}
e.preventDefault();
inp.x = clamp(inp.x + dx, 0, W);
inp.y = clamp(inp.y + dy, 0, H);
inp.vx = dx * 0.5;
inp.vy = dy * 0.5;
inp.idle = 0;
refresh();
});
listen(window, 'resize', function (): void {
fit();
show();
});
if (!reduce) {
rafId = requestAnimationFrame(tick);
}
return function (): void {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) {
cleaners[i]();
}
};
}
const TRAIL_LEN = 16;
const GLOW_BLUR = 9;
const FADE_ALPHA = 0.86;
const HEAD_R = 2.1;
const BURST_GAP = 44;
const SPARK_N = 56;
const SPARK_DRAG = 0.972;
const SPARK_GRAVITY = 0.045;
const PREWARM_STEPS = 38;
const TXT_AUTO = '꼬리 이력을 가산 합성으로 겹친다 — 겹친 곳이 흰빛으로 번진다';
const TXT_TAP = '누른 자리에서 빛무리가 터진다';
interface Spark { x: number; y: number; vx: number; vy: number; age: number; life: number; hist: number[]; hue: number; }
// 위치 이력 한 줄에서 i 번째 점의 알파 — 머리에서 멀수록 FADE_ALPHA 를 거듭 곱한다
function trailAlpha(back: number): number {
return Math.pow(FADE_ALPHA, back);
}
function makeScene(inp: Input, reduce: boolean): Scene {
const rng = lcg(4004);
let sparks: Spark[] = [];
let gap = 2;
let colorIdx = 0;
const glows: HTMLCanvasElement[] = [];
function glowFor(idx: number): HTMLCanvasElement {
if (glows[idx]) {
return glows[idx];
}
const size = GLOW_BLUR * 4;
const cv = document.createElement('canvas');
cv.width = size;
cv.height = size;
const c = cv.getContext('2d');
if (c) {
const g = c.createRadialGradient(size / 2, size / 2, 0, size / 2, size / 2, size / 2);
g.addColorStop(0, rgba(CREAM, 0.9));
g.addColorStop(0.25, rgba(PALETTE[idx], 0.45));
g.addColorStop(1, rgba(PALETTE[idx], 0));
c.fillStyle = g;
c.fillRect(0, 0, size, size);
}
glows[idx] = cv;
return cv;
}
function burst(x: number, y: number): void {
const hue = colorIdx % PALETTE.length;
colorIdx += 1;
for (let i = 0; i < SPARK_N; i += 1) {
const a = rng() * PI2;
const sp = 2.2 + rng() * 2.4;
sparks.push({ x: x, y: y, vx: Math.cos(a) * sp, vy: Math.sin(a) * sp, age: 0, life: 70 + rng() * 26, hist: [], hue: i % 4 === 0 ? (hue + 1) % PALETTE.length : hue });
}
if (sparks.length > 330) {
sparks.splice(0, sparks.length - 330);
}
}
const scene: Scene = {
step(): void {
gap -= 1;
if (gap <= 0) {
burst(90 + rng() * 300, 80 + rng() * 70);
gap = BURST_GAP;
}
const alive: Spark[] = [];
for (let i = 0; i < sparks.length; i += 1) {
const s = sparks[i];
s.age += 1;
s.hist.push(s.x, s.y);
if (s.hist.length > TRAIL_LEN * 2) {
s.hist.splice(0, 2);
}
s.vx *= SPARK_DRAG;
s.vy = s.vy * SPARK_DRAG + SPARK_GRAVITY;
s.x += s.vx;
s.y += s.vy;
if (s.age < s.life) {
alive.push(s);
}
}
sparks = alive;
},
draw(ctx: CanvasRenderingContext2D): void {
drawSky(ctx, H);
// 이 항목의 핵심 — 합성 방식을 가산으로 바꾸면 겹친 곳의 색이 더해져 하얗게 번진다
ctx.globalCompositeOperation = 'lighter';
ctx.lineCap = 'round';
for (let i = 0; i < sparks.length; i += 1) {
const s = sparks[i];
const life = Math.pow(1 - s.age / s.life, 0.7);
const n = s.hist.length / 2;
for (let k = 1; k < n; k += 1) {
const a = trailAlpha(n - k) * life;
ctx.strokeStyle = rgba(PALETTE[s.hue], a * 0.85);
ctx.lineWidth = lerp(0.6, HEAD_R * 1.3, k / n);
ctx.beginPath();
ctx.moveTo(s.hist[(k - 1) * 2], s.hist[(k - 1) * 2 + 1]);
ctx.lineTo(s.hist[k * 2], s.hist[k * 2 + 1]);
ctx.stroke();
}
const r = GLOW_BLUR * (0.6 + 0.4 * life);
ctx.globalAlpha = life * (reduce ? 0.6 : 0.85);
ctx.drawImage(glowFor(s.hue), s.x - r, s.y - r, r * 2, r * 2);
ctx.globalAlpha = 1;
ctx.fillStyle = rgba(CREAM, life);
ctx.beginPath();
ctx.arc(s.x, s.y, HEAD_R * (0.5 + 0.5 * life), 0, PI2);
ctx.fill();
}
ctx.globalCompositeOperation = 'source-over';
},
label(): string {
return inp.idle < IDLE_TICKS ? TXT_TAP : TXT_AUTO;
},
tap(): void {
burst(inp.x, inp.y);
}
};
for (let i = 0; i < PREWARM_STEPS; i += 1) {
scene.step();
}
return scene;
}
export default function FwAdditiveTrailHistoryGlow() {
const rootRef = useRef<HTMLDivElement | null>(null);
const canvasRef = useRef<HTMLCanvasElement | null>(null);
const statusRef = useRef<HTMLParagraphElement | null>(null);
const btnRef = useRef<HTMLButtonElement | null>(null);
useEffect(() => {
const root = rootRef.current;
const canvas = canvasRef.current;
const statusEl = statusRef.current;
const btnEl = btnRef.current;
if (!root || !canvas || !statusEl || !btnEl) return;
return start(root, canvas, statusEl, btnEl, makeScene);
}, []);
return (
<main className={styles.stage}>
<div className={`${styles.sc} is-demo`} ref={rootRef}>
<canvas className={styles.sc__canvas} ref={canvasRef} width={480} height={300} tabIndex={0} aria-label="과거 위치 이력을 잇고 겹칠수록 밝아지는 꼬리와 빛무리" />
<p className={styles.sc__status} ref={statusRef} aria-live="polite">꼬리 이력을 가산 합성으로 겹친다 — 겹친 곳이 흰빛으로 번진다</p>
<button className={styles.sc__btn} ref={btnRef} type="button">멈춤</button>
<p className={styles.sc__caption}>과거 위치 이력을 잇고 겹칠수록 밝아지는 꼬리와 빛무리</p>
</div>
</main>
);
}04 Tails Drawn From Position History and a Glow That Brightens Where They Overlap — Measured area 41.561% · moving frames 23/23Original by GODRICH · SCSS and React ship in the zip · CSS Fireworks: 9 Bursts, Trails and Reflections
The post this demo lives in
CSS Fireworks: 9 Bursts, Trails and ReflectionsBefore a css fireworks burst can pop, hundreds of grain paths have to be decided first — scene 01's sphere spread and sc See all demos in this post
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