Have you ever been mesmerized by abstract particle animations? These flowing, dynamic visuals can be achieved with surprisingly simple techniques using plain JavaScript and the HTML canvas element. In this article, we will break down the process of creating a flow field that animates thousands of particles, giving them a natural movement.
To start, we need three files: an HTML file to set up the canvas, a CSS file for styling, and a JavaScript file for handling the logic.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Flow Fields</title>
<link rel="stylesheet" href="styles.css">
</head>
<body>
<canvas id="canvas1"></canvas>
<script src="script.js"></script>
</body>
</html>
Let’s add a simple style to give our canvas a black background and make sure all padding and margins are removed.
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
canvas {
background-color: black;
}
The Particle class is where the core of the animation lies. Each particle moves across the canvas, leaving a trail of its past locations, creating the flowing effect.
class Particle {
constructor(effect) {
this.effect = effect;
this.x = Math.floor(Math.random() * this.effect.width);
this.y = Math.floor(Math.random() * this.effect.height);
this.speedModifier = Math.floor(Math.random() * 5 + 1);
this.history = [{ x: this.x, y: this.y }];
this.maxLength = Math.floor(Math.random() * 200 + 10);
this.timer = this.maxLength * 2;
this.colors = ['#4C026B', '#8E0E00', '#9D0208', '#BA1A1A', '#730D9E'];
this.color = this.colors[Math.floor(Math.random() * this.colors.length)];
}
draw(context) {
context.beginPath();
context.moveTo(this.history[0].x, this.history[0].y);
for (let i = 1; i < this.history.length; i++) {
context.lineTo(this.history[i].x, this.history[i].y);
}
context.strokeStyle = this.color;
context.stroke();
}
update() {
this.timer--;
if (this.timer >= 1) {
let x = Math.floor(this.x / this.effect.cellSize);
let y = Math.floor(this.y / this.effect.cellSize);
let index = y * this.effect.cols + x;
let angle = this.effect.flowField[index];
this.speedX = Math.cos(angle);
this.speedY = Math.sin(angle);
this.x += this.speedX * this.speedModifier;
this.y += this.speedY * this.speedModifier;
this.history.push({ x: this.x, y: this.y });
if (this.history.length > this.maxLength) {
this.history.shift();
}
} else if (this.history.length > 1) {
this.history.shift();
} else {
this.reset();
}
}
reset() {
this.x = Math.floor(Math.random() * this.effect.width);
this.y = Math.floor(Math.random() * this.effect.height);
this.history = [{ x: this.x, y: this.y }];
this.timer = this.maxLength * 2;
}
}
The Effect class handles the creation of particles and the flow field itself, which controls the movement of the particles.
class Effect {
constructor(canvas) {
this.canvas = canvas;
this.width = this.canvas.width;
this.height = this.canvas.height;
this.particles = [];
this.numberOfParticles = 3000;
this.cellSize = 20;
this.flowField = [];
this.curve = 5;
this.zoom = 0.12;
this.debug = true;
this.init();
}
init() {
this.rows = Math.floor(this.height / this.cellSize);
this.cols = Math.floor(this.width / this.cellSize);
for (let y = 0; y < this.rows; y++) {
for (let x = 0; x < this.cols; x++) {
let angle = (Math.cos(x * this.zoom) + Math.sin(y * this.zoom)) * this.curve;
this.flowField.push(angle);
}
}
for (let i = 0; i < this.numberOfParticles; i++) {
this.particles.push(new Particle(this));
}
}
drawGrid(context) {
context.save();
context.strokeStyle = 'white';
context.lineWidth = 0.3;
for (let c = 0; c < this.cols; c++) {
context.beginPath();
context.moveTo(c * this.cellSize, 0);
context.lineTo(c * this.cellSize, this.height);
context.stroke();
}
for (let r = 0; r < this.rows; r++) {
context.beginPath();
context.moveTo(0, r * this.cellSize);
context.lineTo(this.width, r * this.cellSize);
context.stroke();
}
context.restore();
}
render(context) {
if (this.debug) this.drawGrid(context);
this.particles.forEach(particle => {
particle.draw(context);
particle.update();
});
}
}
To make everything work, we need an animation loop that continuously clears the canvas and re-renders the particles:
const effect = new Effect(canvas);
function animate() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
effect.render(ctx);
requestAnimationFrame(animate);
}
animate();
By breaking down the Particle and Effect classes, we have created a fluid and dynamic flow field animation using only vanilla JavaScript. The simplicity of the HTML canvas, combined with JavaScript's trigonometric functions, allows us to build these mesmerizing visual effects.
Feel free to play around with the particle count, colors, or the flow field formula to create your own unique effects!
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