509 lines
17 KiB
JavaScript
509 lines
17 KiB
JavaScript
/**
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* FlowFieldBackground
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*
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* Minimal generative backdrop: hundreds of hair-thin particles ride a
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* domain-warped simplex flow field and leave short silk-like trails.
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* The cursor bends the current into a slow vortex (nearby strokes pick up
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* a faint glow); clicking / tapping emits a thin ripple that shoves
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* particles aside.
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*
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* Trails are drawn by erasing the previous frame with a low-alpha
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* `destination-out` pass, so the CSS gradient painted behind the canvas
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* element keeps showing through instead of being flooded by an opaque fill.
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*/
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/* Deterministic PRNG so the noise permutation is stable within a page load. */
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function mulberry32(seed) {
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return function () {
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seed |= 0;
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seed = (seed + 0x6D2B79F5) | 0;
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let t = Math.imul(seed ^ (seed >>> 15), 1 | seed);
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t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
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return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
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};
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}
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/* Compact seeded 2D simplex noise (Gustavson-style), output in ~[-1, 1]. */
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class SimplexNoise {
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constructor(seed) {
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const rand = mulberry32(seed);
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const p = new Uint8Array(256);
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for (let i = 0; i < 256; i++) p[i] = i;
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// Fisher-Yates shuffle for the permutation table.
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for (let i = 255; i > 0; i--) {
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const j = (rand() * (i + 1)) | 0;
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const tmp = p[i];
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p[i] = p[j];
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p[j] = tmp;
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}
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this.perm = new Uint8Array(512);
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this.permMod12 = new Uint8Array(512);
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for (let i = 0; i < 512; i++) {
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this.perm[i] = p[i & 255];
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this.permMod12[i] = this.perm[i] % 12;
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}
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}
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noise2D(xin, yin) {
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const F2 = SimplexNoise.F2;
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const G2 = SimplexNoise.G2;
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const GRAD3 = SimplexNoise.GRAD3;
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let n0 = 0, n1 = 0, n2 = 0;
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const s = (xin + yin) * F2;
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const i = Math.floor(xin + s);
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const j = Math.floor(yin + s);
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const t = (i + j) * G2;
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const x0 = xin - (i - t);
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const y0 = yin - (j - t);
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// Corner offsets depend on which half of the simplex we landed in.
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let i1, j1;
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if (x0 > y0) { i1 = 1; j1 = 0; } else { i1 = 0; j1 = 1; }
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const x1 = x0 - i1 + G2;
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const y1 = y0 - j1 + G2;
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const x2 = x0 - 1 + 2 * G2;
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const y2 = y0 - 1 + 2 * G2;
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const ii = i & 255;
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const jj = j & 255;
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let t0 = 0.5 - x0 * x0 - y0 * y0;
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if (t0 >= 0) {
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const g = GRAD3[this.permMod12[ii + this.perm[jj]]];
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t0 *= t0;
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n0 = t0 * t0 * (g[0] * x0 + g[1] * y0);
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}
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let t1 = 0.5 - x1 * x1 - y1 * y1;
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if (t1 >= 0) {
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const g = GRAD3[this.permMod12[ii + i1 + this.perm[jj + j1]]];
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t1 *= t1;
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n1 = t1 * t1 * (g[0] * x1 + g[1] * y1);
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}
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let t2 = 0.5 - x2 * x2 - y2 * y2;
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if (t2 >= 0) {
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const g = GRAD3[this.permMod12[ii + 1 + this.perm[jj + 1]]];
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t2 *= t2;
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n2 = t2 * t2 * (g[0] * x2 + g[1] * y2);
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}
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// Empirical factor scaling the sum into roughly [-1, 1].
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return 70 * (n0 + n1 + n2);
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}
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}
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SimplexNoise.F2 = 0.5 * (Math.sqrt(3) - 1);
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SimplexNoise.G2 = (3 - Math.sqrt(3)) / 6;
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SimplexNoise.GRAD3 = [
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[1, 1], [-1, 1], [1, -1], [-1, -1],
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[1, 0], [-1, 0], [1, 0], [-1, 0],
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[0, 1], [0, -1], [0, 1], [0, -1]
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];
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class FlowFieldBackground {
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constructor() {
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// Legacy element id kept from the previous background; the canvas
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// and its CSS (css/matrix.css) are reused on purpose.
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this.canvas = document.getElementById('matrixCanvas');
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this.ctx = this.canvas.getContext('2d');
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this.noise = new SimplexNoise((Math.random() * 0xffffffff) | 0);
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this.particles = [];
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this.sparks = [];
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this.mouse = { x: 0, y: 0, active: false };
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this.rafId = null;
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this.prefersReducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
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this.width = 0;
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this.height = 0;
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this.dpr = 1;
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// Random phase so each visit opens on a different current.
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this.time = Math.random() * 4000;
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this.config = {
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baseSpeed: 0.75,
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maxSpeed: 2.8, // velocity cap so streaks remain calm
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steer: 0.055, // how fast particles align with the field
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fieldScale: 0.0015, // noise zoom: small value = large, calm features
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warpStrength: 160, // px of domain warp, keeps the flow organic
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winding: 2.4, // field angle range multiplier (x PI)
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timeDrift: 0.00028, // slow evolution of the whole field
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fadeAlpha: 0.038, // trail persistence (lower = longer trails)
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mouseRadius: 180,
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mouseSwirl: 0.5, // tangential push around the cursor
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mousePull: 0.06, // whisper of inward pull -> orbiting feel
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glowBoost: 0.25, // extra alpha for particles near the cursor
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sparkCount: 10, // subtle micro-sparks per click
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life: { min: 280, max: 920 } // frames before a particle respawns
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};
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// Rich site palette with cyan, indigo, violet, and soft luminous accents
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this.palette = [
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{ weight: 0.55, rgb: '206, 224, 255', alpha: 0.13 }, // Soft cyan-white
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{ weight: 0.18, rgb: '79, 195, 247', alpha: 0.24 }, // Electric cyan
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{ weight: 0.14, rgb: '102, 126, 234', alpha: 0.16 }, // Deep indigo
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{ weight: 0.13, rgb: '146, 103, 197', alpha: 0.16 } // Soft violet
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];
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this.init();
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}
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init() {
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this.bindEvents();
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this.handleResize();
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if (this.prefersReducedMotion) {
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// Single long-exposure render; no animation loop at all.
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this.warmup(180);
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return;
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}
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// Pre-run a short exposure so the first paint is already textured.
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this.warmup(60);
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this.animate();
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}
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bindEvents() {
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// The canvas has pointer-events: none, so listen on window.
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window.addEventListener('pointermove', (e) => {
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this.mouse.x = e.clientX;
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this.mouse.y = e.clientY;
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this.mouse.active = true;
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}, { passive: true });
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window.addEventListener('pointerdown', (e) => {
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this.spawnClickBurst(e.clientX, e.clientY);
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}, { passive: true });
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window.addEventListener('pointerout', () => {
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this.mouse.active = false;
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});
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// Pause the rAF loop when the tab is hidden to save CPU / battery.
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document.addEventListener('visibilitychange', () => {
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if (document.hidden) {
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this.stop();
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} else if (!this.prefersReducedMotion) {
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this.start();
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}
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});
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let resizeRaf = null;
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window.addEventListener('resize', () => {
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if (resizeRaf) cancelAnimationFrame(resizeRaf);
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resizeRaf = requestAnimationFrame(() => this.handleResize());
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});
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}
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start() {
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if (this.rafId) return;
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this.animate();
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}
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stop() {
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if (this.rafId) {
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cancelAnimationFrame(this.rafId);
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this.rafId = null;
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}
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}
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handleResize() {
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const w = window.innerWidth;
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const h = window.innerHeight;
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// Mobile browsers fire resize on scroll when the URL bar collapses;
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// only react to real geometry changes to avoid canvas flicker.
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if (this.width && w === this.width && Math.abs(h - this.height) < 150) return;
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this.width = w;
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this.height = h;
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this.dpr = Math.min(window.devicePixelRatio || 1, 2);
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this.canvas.width = Math.round(w * this.dpr);
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this.canvas.height = Math.round(h * this.dpr);
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this.ctx.setTransform(this.dpr, 0, 0, this.dpr, 0, 0);
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// Density scales with area, clamped for both phones and ultrawides.
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const count = Math.round(Math.min(Math.max((w * h) / 2600, 160), 650));
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this.particles = [];
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for (let i = 0; i < count; i++) {
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this.particles.push(this.createParticle());
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}
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// Repaint a short exposure so a resize never flashes an empty canvas.
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this.warmup(30);
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}
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pickTone() {
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let roll = Math.random();
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for (const tone of this.palette) {
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roll -= tone.weight;
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if (roll <= 0) return tone;
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}
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return this.palette[0];
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}
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createParticle() {
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const tone = this.pickTone();
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const { min, max } = this.config.life;
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// 3 Depth layers: 0 (background ambient), 1 (main stream), 2 (foreground highlight)
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const randDepth = Math.random();
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let depth = 1;
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let speedMult = 1.0;
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let widthMult = 1.0;
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let alphaMult = 1.0;
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if (randDepth < 0.25) {
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depth = 0;
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speedMult = 0.65;
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widthMult = 0.6;
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alphaMult = 0.65;
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} else if (randDepth > 0.78) {
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depth = 2;
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speedMult = 1.35;
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widthMult = 1.35;
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alphaMult = 1.25;
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}
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return {
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depth,
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x: Math.random() * this.width,
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y: Math.random() * this.height,
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px: 0,
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py: 0,
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vx: 0,
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vy: 0,
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speed: this.config.baseSpeed * speedMult * (0.75 + Math.random() * 0.5),
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width: (0.7 + Math.random() * 0.5) * widthMult,
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rgb: tone.rgb,
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baseAlpha: tone.alpha * (0.75 + Math.random() * 0.5) * alphaMult,
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alpha: 0,
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glow: 0,
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life: Math.floor(Math.random() * (min * 0.5)),
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maxLife: min + Math.random() * (max - min),
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fresh: true // no previous point yet -> nothing to draw
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};
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}
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respawn(p) {
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p.x = Math.random() * this.width;
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p.y = Math.random() * this.height;
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p.vx = 0;
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p.vy = 0;
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p.life = 0;
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p.fresh = true;
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}
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spawnClickBurst(x, y) {
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// Emit a subtle, delicate burst of hair-thin micro-sparks on click
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const count = this.config.sparkCount;
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for (let i = 0; i < count; i++) {
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const angle = Math.random() * Math.PI * 2;
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const speed = 1.0 + Math.random() * 2.2;
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const tone = this.pickTone();
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this.sparks.push({
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x,
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y,
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px: x,
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py: y,
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vx: Math.cos(angle) * speed,
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vy: Math.sin(angle) * speed,
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rgb: tone.rgb,
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size: 0.6 + Math.random() * 0.8,
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alpha: 0.6 + Math.random() * 0.25,
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life: 0,
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maxLife: 25 + Math.random() * 25
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});
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}
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}
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updateParticles() {
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const { fieldScale, warpStrength, winding, steer, maxSpeed } = this.config;
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const t = this.time;
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const m = this.mouse;
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const radius = this.config.mouseRadius;
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const radiusSq = radius * radius;
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const fadeIn = 35;
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const fadeOut = 55;
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for (const p of this.particles) {
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// Smooth life envelope (fade-in on spawn, fade-out near maxLife)
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let lifeEnvelope = 1;
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if (p.life < fadeIn) {
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lifeEnvelope = p.life / fadeIn;
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} else if (p.life > p.maxLife - fadeOut) {
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lifeEnvelope = Math.max(0, (p.maxLife - p.life) / fadeOut);
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}
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p.alpha = p.baseAlpha * lifeEnvelope;
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// Domain-warped flow angle: the warp layer bends the main field
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// so the current curls organically instead of drifting straight.
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const warp = this.noise.noise2D(
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p.x * fieldScale * 0.4 + t * 0.5,
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p.y * fieldScale * 0.4 - t * 0.3
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);
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const angle = this.noise.noise2D(
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(p.x + warp * warpStrength) * fieldScale + t,
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(p.y - warp * warpStrength) * fieldScale - t * 0.7
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) * Math.PI * winding;
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p.vx += (Math.cos(angle) * p.speed - p.vx) * steer;
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p.vy += (Math.sin(angle) * p.speed - p.vy) * steer;
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// Cursor vortex: tangential swirl + slight inward pull.
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let proximity = 0;
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if (m.active) {
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const dx = p.x - m.x;
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const dy = p.y - m.y;
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const distSq = dx * dx + dy * dy;
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if (distSq < radiusSq && distSq > 0.5) {
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const dist = Math.sqrt(distSq);
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proximity = 1 - dist / radius;
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const falloff = proximity * proximity;
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p.vx += (-dy / dist) * falloff * this.config.mouseSwirl
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+ (-dx / dist) * falloff * this.config.mousePull;
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p.vy += (dx / dist) * falloff * this.config.mouseSwirl
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+ (-dy / dist) * falloff * this.config.mousePull;
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}
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}
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// Smooth the glow so the highlight eases in and out.
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p.glow += (proximity - p.glow) * 0.12;
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const speedSq = p.vx * p.vx + p.vy * p.vy;
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if (speedSq > maxSpeed * maxSpeed) {
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const scale = maxSpeed / Math.sqrt(speedSq);
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p.vx *= scale;
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p.vy *= scale;
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}
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p.px = p.x;
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p.py = p.y;
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p.x += p.vx;
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p.y += p.vy;
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// Wrap at the edges; mark fresh so no cross-screen streak is drawn.
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if (p.x < 0 || p.x > this.width || p.y < 0 || p.y > this.height) {
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p.x = (p.x + this.width) % this.width;
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p.y = (p.y + this.height) % this.height;
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p.fresh = true;
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}
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if (++p.life > p.maxLife) {
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this.respawn(p);
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}
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}
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}
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updateSparks() {
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const drag = 0.91;
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const { fieldScale } = this.config;
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const t = this.time;
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for (let i = this.sparks.length - 1; i >= 0; i--) {
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const s = this.sparks[i];
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s.px = s.x;
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s.py = s.y;
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// Gently blend spark velocity with noise field as it slows down
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const angle = this.noise.noise2D(s.x * fieldScale + t, s.y * fieldScale - t) * Math.PI * 2;
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s.vx = s.vx * drag + Math.cos(angle) * 0.15;
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s.vy = s.vy * drag + Math.sin(angle) * 0.15;
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s.x += s.vx;
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s.y += s.vy;
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s.life++;
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if (s.life >= s.maxLife) {
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this.sparks.splice(i, 1);
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}
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}
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}
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fade() {
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// Erase a fraction of the previous frame towards transparency so
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// the CSS backdrop behind the canvas keeps showing through.
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this.ctx.globalCompositeOperation = 'destination-out';
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this.ctx.fillStyle = `rgba(0, 0, 0, ${this.config.fadeAlpha})`;
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this.ctx.fillRect(0, 0, this.width, this.height);
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}
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drawParticles() {
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const ctx = this.ctx;
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// Additive blending gives a soft glow where currents overlap.
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ctx.globalCompositeOperation = 'lighter';
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ctx.lineCap = 'round';
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for (const p of this.particles) {
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if (p.fresh) {
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p.fresh = false;
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continue;
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}
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const alpha = Math.min(1, p.alpha + p.glow * this.config.glowBoost);
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if (alpha <= 0.005) continue;
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ctx.strokeStyle = `rgba(${p.rgb}, ${alpha.toFixed(3)})`;
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ctx.lineWidth = p.width;
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ctx.beginPath();
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ctx.moveTo(p.px, p.py);
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ctx.lineTo(p.x, p.y);
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ctx.stroke();
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// Draw a subtle bright dot at the head of foreground particles
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if (p.depth === 2 && (p.glow > 0.1 || Math.random() < 0.12)) {
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ctx.fillStyle = `rgba(240, 248, 255, ${(alpha * 0.75).toFixed(3)})`;
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ctx.beginPath();
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ctx.arc(p.x, p.y, p.width * 0.75, 0, Math.PI * 2);
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ctx.fill();
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}
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}
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}
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drawSparks() {
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if (!this.sparks.length) return;
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const ctx = this.ctx;
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ctx.globalCompositeOperation = 'lighter';
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for (const s of this.sparks) {
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const lifeRatio = 1 - s.life / s.maxLife;
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const alpha = (s.alpha * lifeRatio * lifeRatio).toFixed(3);
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if (alpha <= 0) continue;
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ctx.strokeStyle = `rgba(${s.rgb}, ${alpha})`;
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ctx.lineWidth = s.size * lifeRatio;
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ctx.beginPath();
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ctx.moveTo(s.px, s.py);
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ctx.lineTo(s.x, s.y);
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ctx.stroke();
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}
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}
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|
step(withFade) {
|
|
if (withFade) this.fade();
|
|
this.updateSparks();
|
|
this.updateParticles();
|
|
this.drawParticles();
|
|
this.drawSparks();
|
|
this.time += this.config.timeDrift;
|
|
}
|
|
|
|
warmup(steps) {
|
|
for (let i = 0; i < steps; i++) {
|
|
this.step(false);
|
|
}
|
|
}
|
|
|
|
animate() {
|
|
this.step(true);
|
|
this.rafId = requestAnimationFrame(() => this.animate());
|
|
}
|
|
}
|
|
|
|
document.addEventListener('DOMContentLoaded', () => {
|
|
new FlowFieldBackground();
|
|
});
|