xmichaelx/dla.js

## dla.js
function createField(width, height) {
	var field = new Uint8Array(width * height);
	var fcenterX = Math.floor(width / 2);
	var fcenterY = Math.floor(height / 2);

	// center occupied
	field[fcenterX + fcenterY * width] = 1;

	return { field: field, width:width, height:height};
}

function createParticles(field, particleCount) {
	var particlesX = new Uint16Array(particleCount);
	var particlesY = new Uint16Array(particleCount);
	var particlesStuck = new Uint8Array(particleCount);

	return { x: particlesX, y:particlesY, stuck: particlesStuck, count: particleCount};
}


function resetSingleParticle(particles, field, i) {
	var x = Math.floor(Math.random() * width);
	var y = Math.floor(Math.random() * height);

	while(field[y*width+x]) {
		x = Math.floor(Math.random() * width);
		y = Math.floor(Math.random() * height);
	}

	particles.x[i] = x;
	particles.y[i] = y;
}


function resetAllParticles(particles, field) {
	for (var i=0;i<particles.count;i++) {
		resetSingleParticle(particles, field, i);
	}
}

function alone(particles, field, i) {
	var cx = particles.x[i];
	var cy = particles.y[i];

	var lx = cx - 1;
	var rx = cx + 1;
	var ty = cy - 1;
	var by = cy + 1;

	if (cx <= 0 || cx >= field.width ||
		lx <= 0 || lx >= field.width ||
		rx <= 0 || rx >= field.width ||
		cy <= 0 || cy >= field.height ||
		ty <= 0 || ty >= field.height ||
		by <= 0 || by >= field.height) {
		return true;
	}

	cy *= field.width;
	by *= field.width;
	ty *= field.width;

	if (field.field[cx + ty] ||
		field.field[lx + cy] ||
		field.field[rx + cy] ||
		field.field[cx + by]) {
		return false;
	}

	if (field.field[lx + ty] ||
		field.field[lx + by] ||
		field.field[rx + ty] ||
		field.field[rx + by]) {
		return false;
	}

	return true;
}

function updateSingleParticle(particles,field, i) {
	if (particles.stuck[i] == 0) {
		var x = particles.x[i];
		var y = particles.y[i];

		x += Math.random() > 0.5 ? 1 : -1;
		y += Math.random() > 0.5 ? 1 : -1;

		if ( (x < 0) || (y < 0) || (x >= field.width) || (y >= field.height)) {
			resetSingleParticle(particles, field, i);
		}

        particles.x[i] = x;
        particles.y[i] = y;

		if (!alone(particles, field, i)) {
			particles.stuck[i] = 1;
			field.field[y*field.width + x] = 1;
		}
	}
}

function step(particles, field) {
	for (var i = 0;i<particles.count;i++) {
		updateSingleParticle(particles, field, i);
	}
}

function createCanvas(width, height) {
	var canvas = document.createElement("canvas");
	document.body.appendChild(canvas);
	canvas.width = width;
	canvas.height = height;

	return canvas;
}


function paint(field, canvas, particles) {
	var ctx = canvas.getContext('2d');
	ctx.clearRect ( 0 , 0 , field.width, field.height );
	var imageData = ctx.getImageData(0, 0, field.width, field.height);

	var data = imageData.data;

	for (var i=0;i<particles.count;i++) {
		var x = particles.x[i];
		var y = particles.y[i];
		var stuck = particles.stuck[i];

		var fieldIndex = y * field.width + x;
    	var index = fieldIndex * 4;
    	var value = stuck ? 0 : 127;
    	data[index]   = value;	// red
        data[++index] = value;	// green
        data[++index] = value;	// blue
        data[++index] = 255;	// alpha
	}

	ctx.putImageData(imageData, 0, 0);
}


var particleCount = 40000;
var width = 500;
var height = 500;


var canvas = createCanvas(width, height);
var field = createField(width, height);
var particles = createParticles(field, particleCount);
resetAllParticles(particles,field);


setInterval(function() {
	for (var i = 0;i < 4;i++) {
		step(particles, field);
	}

	paint(field, canvas, particles);
} , 33);

## index.html
<!doctype html>

<html lang="en">
<head>
  <meta charset="utf-8">

  <title>Diffusion-Limited aggregation</title>
  <meta name="description" content="Diffusion-Limited aggregation">
  <meta name="author" content="Michal Drzal">
</head>

<body>
  <script src="dla.js"></script>
</canvas>

</body>
</html>
	function createField(width, height) {
	var field = new Uint8Array(width * height);
	var fcenterX = Math.floor(width / 2);
	var fcenterY = Math.floor(height / 2);

	// center occupied
	field[fcenterX + fcenterY * width] = 1;

	return { field: field, width:width, height:height};
	}

	function createParticles(field, particleCount) {
	var particlesX = new Uint16Array(particleCount);
	var particlesY = new Uint16Array(particleCount);
	var particlesStuck = new Uint8Array(particleCount);

	return { x: particlesX, y:particlesY, stuck: particlesStuck, count: particleCount};
	}


	function resetSingleParticle(particles, field, i) {
	var x = Math.floor(Math.random() * width);
	var y = Math.floor(Math.random() * height);

	while(field[y*width+x]) {
	x = Math.floor(Math.random() * width);
	y = Math.floor(Math.random() * height);
	}

	particles.x[i] = x;
	particles.y[i] = y;
	}


	function resetAllParticles(particles, field) {
	for (var i=0;i<particles.count;i++) {
	resetSingleParticle(particles, field, i);
	}
	}

	function alone(particles, field, i) {
	var cx = particles.x[i];
	var cy = particles.y[i];

	var lx = cx - 1;
	var rx = cx + 1;
	var ty = cy - 1;
	var by = cy + 1;

	if (cx <= 0 \|\| cx >= field.width \|\|
	lx <= 0 \|\| lx >= field.width \|\|
	rx <= 0 \|\| rx >= field.width \|\|
	cy <= 0 \|\| cy >= field.height \|\|
	ty <= 0 \|\| ty >= field.height \|\|
	by <= 0 \|\| by >= field.height) {
	return true;
	}

	cy *= field.width;
	by *= field.width;
	ty *= field.width;

	if (field.field[cx + ty] \|\|
	field.field[lx + cy] \|\|
	field.field[rx + cy] \|\|
	field.field[cx + by]) {
	return false;
	}

	if (field.field[lx + ty] \|\|
	field.field[lx + by] \|\|
	field.field[rx + ty] \|\|
	field.field[rx + by]) {
	return false;
	}

	return true;
	}

	function updateSingleParticle(particles,field, i) {
	if (particles.stuck[i] == 0) {
	var x = particles.x[i];
	var y = particles.y[i];

	x += Math.random() > 0.5 ? 1 : -1;
	y += Math.random() > 0.5 ? 1 : -1;

	if ( (x < 0) \|\| (y < 0) \|\| (x >= field.width) \|\| (y >= field.height)) {
	resetSingleParticle(particles, field, i);
	}

	particles.x[i] = x;
	particles.y[i] = y;

	if (!alone(particles, field, i)) {
	particles.stuck[i] = 1;
	field.field[y*field.width + x] = 1;
	}
	}
	}

	function step(particles, field) {
	for (var i = 0;i<particles.count;i++) {
	updateSingleParticle(particles, field, i);
	}
	}

	function createCanvas(width, height) {
	var canvas = document.createElement("canvas");
	document.body.appendChild(canvas);
	canvas.width = width;
	canvas.height = height;

	return canvas;
	}


	function paint(field, canvas, particles) {
	var ctx = canvas.getContext('2d');
	ctx.clearRect ( 0 , 0 , field.width, field.height );
	var imageData = ctx.getImageData(0, 0, field.width, field.height);

	var data = imageData.data;

	for (var i=0;i<particles.count;i++) {
	var x = particles.x[i];
	var y = particles.y[i];
	var stuck = particles.stuck[i];

	var fieldIndex = y * field.width + x;
	var index = fieldIndex * 4;
	var value = stuck ? 0 : 127;
	data[index] = value; // red
	data[++index] = value; // green
	data[++index] = value; // blue
	data[++index] = 255; // alpha
	}

	ctx.putImageData(imageData, 0, 0);
	}


	var particleCount = 40000;
	var width = 500;
	var height = 500;


	var canvas = createCanvas(width, height);
	var field = createField(width, height);
	var particles = createParticles(field, particleCount);
	resetAllParticles(particles,field);


	setInterval(function() {
	for (var i = 0;i < 4;i++) {
	step(particles, field);
	}

	paint(field, canvas, particles);
	} , 33);
	<!doctype html>

	<html lang="en">
	<head>
	<meta charset="utf-8">

	<title>Diffusion-Limited aggregation</title>
	<meta name="description" content="Diffusion-Limited aggregation">
	<meta name="author" content="Michal Drzal">
	</head>

	<body>
	<script src="dla.js"></script>
	</canvas>

	</body>
	</html>