Flocking
Demonstration of Craig Reynolds' "Flocking" behavior. See: http://www.red3d.com/cwr/ Rules: Cohesion, Separation, Alignment (from natureofcode.com). Drag mouse to add boids into the system.
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let flock;
function setup() {
createCanvas(640, 360);
createP("Drag the mouse to generate new boids.");
flock = new Flock();
// Add an initial set of boids into the system
for (let i = 0; i < 100; i++) {
let b = new Boid(width / 2,height / 2);
flock.addBoid(b);
}
}
function draw() {
background(51);
flock.run();
}
// Add a new boid into the System
function mouseDragged() {
flock.addBoid(new Boid(mouseX, mouseY));
}
// The Nature of Code
// Daniel Shiffman
// http://natureofcode.com
// Flock object
// Does very little, simply manages the array of all the boids
function Flock() {
// An array for all the boids
this.boids = []; // Initialize the array
}
Flock.prototype.run = function() {
for (let i = 0; i < this.boids.length; i++) {
this.boids[i].run(this.boids); // Passing the entire list of boids to each boid individually
}
}
Flock.prototype.addBoid = function(b) {
this.boids.push(b);
}
// The Nature of Code
// Daniel Shiffman
// http://natureofcode.com
// Boid class
// Methods for Separation, Cohesion, Alignment added
function Boid(x, y) {
this.acceleration = createVector(0, 0);
this.velocity = createVector(random(-1, 1), random(-1, 1));
this.position = createVector(x, y);
this.r = 3.0;
this.maxspeed = 3; // Maximum speed
this.maxforce = 0.05; // Maximum steering force
}
Boid.prototype.run = function(boids) {
this.flock(boids);
this.update();
this.borders();
this.render();
}
Boid.prototype.applyForce = function(force) {
// We could add mass here if we want A = F / M
this.acceleration.add(force);
}
// We accumulate a new acceleration each time based on three rules
Boid.prototype.flock = function(boids) {
let sep = this.separate(boids); // Separation
let ali = this.align(boids); // Alignment
let coh = this.cohesion(boids); // Cohesion
// Arbitrarily weight these forces
sep.mult(1.5);
ali.mult(1.0);
coh.mult(1.0);
// Add the force vectors to acceleration
this.applyForce(sep);
this.applyForce(ali);
this.applyForce(coh);
}
// Method to update location
Boid.prototype.update = function() {
// Update velocity
this.velocity.add(this.acceleration);
// Limit speed
this.velocity.limit(this.maxspeed);
this.position.add(this.velocity);
// Reset accelertion to 0 each cycle
this.acceleration.mult(0);
}
// A method that calculates and applies a steering force towards a target
// STEER = DESIRED MINUS VELOCITY
Boid.prototype.seek = function(target) {
let desired = p5.Vector.sub(target,this.position); // A vector pointing from the location to the target
// Normalize desired and scale to maximum speed
desired.normalize();
desired.mult(this.maxspeed);
// Steering = Desired minus Velocity
let steer = p5.Vector.sub(desired,this.velocity);
steer.limit(this.maxforce); // Limit to maximum steering force
return steer;
}
Boid.prototype.render = function() {
// Draw a triangle rotated in the direction of velocity
let theta = this.velocity.heading() + radians(90);
fill(127);
stroke(200);
push();
translate(this.position.x, this.position.y);
rotate(theta);
beginShape();
vertex(0, -this.r * 2);
vertex(-this.r, this.r * 2);
vertex(this.r, this.r * 2);
endShape(CLOSE);
pop();
}
// Wraparound
Boid.prototype.borders = function() {
if (this.position.x < -this.r) this.position.x = width + this.r;
if (this.position.y < -this.r) this.position.y = height + this.r;
if (this.position.x > width + this.r) this.position.x = -this.r;
if (this.position.y > height + this.r) this.position.y = -this.r;
}
// Separation
// Method checks for nearby boids and steers away
Boid.prototype.separate = function(boids) {
let desiredseparation = 25.0;
let steer = createVector(0, 0);
let count = 0;
// For every boid in the system, check if it's too close
for (let i = 0; i < boids.length; i++) {
let d = p5.Vector.dist(this.position,boids[i].position);
// If the distance is greater than 0 and less than an arbitrary amount (0 when you are yourself)
if ((d > 0) && (d < desiredseparation)) {
// Calculate vector pointing away from neighbor
let diff = p5.Vector.sub(this.position, boids[i].position);
diff.normalize();
diff.div(d); // Weight by distance
steer.add(diff);
count++; // Keep track of how many
}
}
// Average -- divide by how many
if (count > 0) {
steer.div(count);
}
// As long as the vector is greater than 0
if (steer.mag() > 0) {
// Implement Reynolds: Steering = Desired - Velocity
steer.normalize();
steer.mult(this.maxspeed);
steer.sub(this.velocity);
steer.limit(this.maxforce);
}
return steer;
}
// Alignment
// For every nearby boid in the system, calculate the average velocity
Boid.prototype.align = function(boids) {
let neighbordist = 50;
let sum = createVector(0,0);
let count = 0;
for (let i = 0; i < boids.length; i++) {
let d = p5.Vector.dist(this.position,boids[i].position);
if ((d > 0) && (d < neighbordist)) {
sum.add(boids[i].velocity);
count++;
}
}
if (count > 0) {
sum.div(count);
sum.normalize();
sum.mult(this.maxspeed);
let steer = p5.Vector.sub(sum, this.velocity);
steer.limit(this.maxforce);
return steer;
} else {
return createVector(0, 0);
}
}
// Cohesion
// For the average location (i.e. center) of all nearby boids, calculate steering vector towards that location
Boid.prototype.cohesion = function(boids) {
let neighbordist = 50;
let sum = createVector(0, 0); // Start with empty vector to accumulate all locations
let count = 0;
for (let i = 0; i < boids.length; i++) {
let d = p5.Vector.dist(this.position,boids[i].position);
if ((d > 0) && (d < neighbordist)) {
sum.add(boids[i].position); // Add location
count++;
}
}
if (count > 0) {
sum.div(count);
return this.seek(sum); // Steer towards the location
} else {
return createVector(0, 0);
}
}
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