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// The Boid class
class Boid {
PVector position;
PVector velocity;
PVector acceleration;
float r;
float maxforce; // Maximum steering force
float maxspeed; // Maximum speed
Boid(float x, float y) {
acceleration = new PVector(0, 0);
// This is a new PVector method not yet implemented in JS
// velocity = PVector.random2D();
// Leaving the code temporarily this way so that this example runs in JS
float angle = random(TWO_PI);
velocity = new PVector(cos(angle), sin(angle));
position = new PVector(x, y);
r = 2.0;
maxspeed = 2;
maxforce = 0.03;
}
void run(ArrayList<Boid> boids) {
flock(boids);
update();
borders();
render();
}
void applyForce(PVector force) {
// We could add mass here if we want A = F / M
acceleration.add(force);
}
// We accumulate a new acceleration each time based on three rules
void flock(ArrayList<Boid> boids) {
PVector sep = separate(boids); // Separation
PVector ali = align(boids); // Alignment
PVector coh = 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
applyForce(sep);
applyForce(ali);
applyForce(coh);
}
// Method to update position
void update() {
// Update velocity
velocity.add(acceleration);
// Limit speed
velocity.limit(maxspeed);
position.add(velocity);
// Reset accelertion to 0 each cycle
acceleration.mult(0);
}
// A method that calculates and applies a steering force towards a target
// STEER = DESIRED MINUS VELOCITY
PVector seek(PVector target) {
PVector desired = PVector.sub(target, position); // A vector pointing from the position to the target
// Scale to maximum speed
desired.normalize();
desired.mult(maxspeed);
// Above two lines of code below could be condensed with new PVector setMag() method
// Not using this method until Processing.js catches up
// desired.setMag(maxspeed);
// Steering = Desired minus Velocity
PVector steer = PVector.sub(desired, velocity);
steer.limit(maxforce); // Limit to maximum steering force
return steer;
}
void render() {
// Draw a triangle rotated in the direction of velocity
float theta = velocity.heading2D() + radians(90);
// heading2D() above is now heading() but leaving old syntax until Processing.js catches up
fill(#f7d709, 100);
//stroke(#211f16, 30);
strokeWeight(3);
pushMatrix();
translate(position.x, position.y);
rotate(theta);
noStroke();
ellipse(r, r, 5, 5);
ellipse(r+5, r, 5, 5);
stroke(0, 80);
line(r, r-5, r+5, r+5);
popMatrix();
}
// Wraparound
void borders() {
if (position.x < -r) position.x = width+r;
if (position.y < -r) position.y = height+r;
if (position.x > width+r) position.x = -r;
if (position.y > height+r) position.y = -r;
}
// Separation
// Method checks for nearby boids and steers away
PVector separate (ArrayList<Boid> boids) {
float desiredseparation = 25.0f;
PVector steer = new PVector(0, 0, 0);
int count = 0;
// For every boid in the system, check if it's too close
for (Boid other : boids) {
float d = PVector.dist(position, other.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
PVector diff = PVector.sub(position, other.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((float)count);
}
// As long as the vector is greater than 0
if (steer.mag() > 0) {
// First two lines of code below could be condensed with new PVector setMag() method
// Not using this method until Processing.js catches up
// steer.setMag(maxspeed);
// Implement Reynolds: Steering = Desired - Velocity
steer.normalize();
steer.mult(maxspeed);
steer.sub(velocity);
steer.limit(maxforce);
}
return steer;
}
// Alignment
// For every nearby boid in the system, calculate the average velocity
PVector align (ArrayList<Boid> boids) {
float neighbordist = 50;
PVector sum = new PVector(0, 0);
int count = 0;
for (Boid other : boids) {
float d = PVector.dist(position, other.position);
if ((d > 0) && (d < neighbordist)) {
sum.add(other.velocity);
count++;
}
}
if (count > 0) {
sum.div((float)count);
// First two lines of code below could be condensed with new PVector setMag() method
// Not using this method until Processing.js catches up
// sum.setMag(maxspeed);
// Implement Reynolds: Steering = Desired - Velocity
sum.normalize();
sum.mult(maxspeed);
PVector steer = PVector.sub(sum, velocity);
steer.limit(maxforce);
return steer;
}
else {
return new PVector(0, 0);
}
}
// Cohesion
// For the average position (i.e. center) of all nearby boids, calculate steering vector towards that position
PVector cohesion (ArrayList<Boid> boids) {
float neighbordist = 50;
PVector sum = new PVector(0, 0); // Start with empty vector to accumulate all positions
int count = 0;
for (Boid other : boids) {
float d = PVector.dist(position, other.position);
if ((d > 0) && (d < neighbordist)) {
sum.add(other.position); // Add position
count++;
}
}
if (count > 0) {
sum.div(count);
return seek(sum); // Steer towards the position
}
else {
return new PVector(0, 0);
}
}
}