live - 60fps 1920 x 1080
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Particle Swarm</title>
<style>
/*
Particle Swarm
--------------
This animation simulates a swirling magnetic field. Thousands of
particles orbit an attractor in the centre of the screen, with a
slight randomness to give the appearance of turbulence. Moving the
mouse changes the location of the attractor so you can manipulate
the particle flow.
*/
html, body {
margin: 0;
padding: 0;
height: 100%;
overflow: hidden;
background: radial-gradient(circle at center, #090a1f, #01030c);
cursor: move;
}
canvas {
display: block;
}
</style>
</head>
<body>
<canvas id="swarm"></canvas>
<script>
(function() {
const canvas = document.getElementById('swarm');
const ctx = canvas.getContext('2d');
function resize() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
}
window.addEventListener('resize', resize);
resize();
// Attractor position; initially centre
const attractor = { x: canvas.width / 2, y: canvas.height / 2 };
document.addEventListener('mousemove', (e) => {
attractor.x = e.clientX;
attractor.y = e.clientY;
});
// Particle definition
class Particle {
constructor() {
this.x = Math.random() * canvas.width;
this.y = Math.random() * canvas.height;
this.vx = 0;
this.vy = 0;
this.colour = `hsl(${Math.random() * 360}, 80%, 60%)`;
}
update() {
// Swirl around the attractor: accelerate perpendicular to the vector
const dx = this.x - attractor.x;
const dy = this.y - attractor.y;
// Invert dx, dy to revolve around centre in clockwise direction
const distSq = dx * dx + dy * dy + 0.01;
const invDist = 1 / Math.sqrt(distSq);
// Perpendicular unit vector (rotate 90 degrees)
const px = -dy * invDist;
const py = dx * invDist;
// Determine base speed inversely proportional to distance
const base = 0.5;
const speed = base * invDist;
this.vx += px * speed + (Math.random() - 0.5) * 0.02;
this.vy += py * speed + (Math.random() - 0.5) * 0.02;
// Dampen velocities to prevent runaway acceleration
this.vx *= 0.98;
this.vy *= 0.98;
this.x += this.vx;
this.y += this.vy;
// Wrap around edges
if (this.x < 0) this.x += canvas.width;
if (this.x > canvas.width) this.x -= canvas.width;
if (this.y < 0) this.y += canvas.height;
if (this.y > canvas.height) this.y -= canvas.height;
}
draw(ctx) {
ctx.fillStyle = this.colour;
ctx.fillRect(this.x, this.y, 1, 1);
}
}
const particleCount = 1200;
const particles = [];
for (let i = 0; i < particleCount; i++) particles.push(new Particle());
function animate() {
ctx.fillStyle = 'rgba(1,3,12,0.2)';
ctx.fillRect(0, 0, canvas.width, canvas.height);
for (const p of particles) {
p.update();
p.draw(ctx);
}
requestAnimationFrame(animate);
}
animate();
})();
</script>
</body>
</html>About this animation
Swarming organic particle behavior.
Under the hood
Flocking Algorithm (Boids)
This utilizes the classic 'Boids' flocking algorithm. Each particle follows three rules: Separation (steer to avoid crowding locals), Alignment (steer towards the average heading of locals), and Cohesion (steer to move toward the average position of locals). The result is organic, bird-like flocking.
