Animating Circles

animating_circles.pde

/* @author: gopal adhikari
I saw an animation like this online several months ago, I cannot remember the site,
but that's where I got the inspiration from.
*/

void setup() {
	size(800, 600);
	noStroke();
	smooth();

	circles = new Circle[MAX_CIRCLES];

	for (int i = 0; i < MAX_CIRCLES; i++) {
		Circle c = new Circle();
		c.radius = random(5, 20);
		c.position = new PVector(random(width), random(height));
		c.velocity = new PVector(random(-0.1, 0.1), random(-0.1, 0.1));
		c.colour = color(#ffffff);
		circles[i] = c;
	}
}

private final int MAX_CIRCLES = 20;
private final float DISTANCE = 125.0;
private final boolean SAVING = false;
private Circle[] circles;

void draw() {

	background(39, 31, 41);

	for (int i = 0; i < MAX_CIRCLES; i++) {

		Circle a = circles[i];

		for (int j = 0; j < MAX_CIRCLES; j++) {

			if (i == j) continue;

			Circle b = circles[j];

			if (PVector.dist(a.position, b.position) < DISTANCE) {
				strokeWeight(2);
				stroke(#ffffff, 60);
				line(a.position.x, a.position.y, b.position.x, b.position.y);
			}

			checkCollision(a);

			a.position.x += a.velocity.x;
			a.position.y += a.velocity.y;

			fill(a.colour, 100);
			ellipse(a.position.x, a.position.y, a.radius, a.radius);
		}
	}

	if (SAVING) saveFrame("f####.gif");

}

void checkCollision(Circle c) {
	if (c.position.x > width || c.position.y > height) {
		c.velocity.rotate(PI / 2.0);
	} else if (c.position.x < 0 || c.position.y < 0) {
		c.velocity.rotate(PI / 2.0);
	}
}

public class Circle {
	PVector position;
	PVector velocity;
	float radius;
	color colour;
}