let target;

​

function setup() {

  createCanvas(400, 400);

  agent = new Agent();

  target = createVector(random(width), random(height));

}

​

function draw() {

  background(220);

​

  agent.update();

  agent.display();

​

  fill(255, 0, 0);

  ellipse(target.x, target.y, 20, 20);

​

  if (dist(agent.pos.x, agent.pos.y, target.x, target.y) < 10) {

    target = createVector(random(width), random(height));

  }

}

​

class Agent {

  constructor() {

    this.pos = createVector(width / 2, height / 2);

    this.vel = createVector();

    this.acc = createVector();

    this.maxSpeed = 2;

    this.kp = 0.05;

    this.ki = 0.001;

    this.kd = 0.01;

    this.prevError = 0;

    this.integral = 0;

  }

​

  update() {

    let desired = createVector(target.x - this.pos.x, target.y - this.pos.y);

    let error = desired.mag();

​

    // P: Proportional term

    let p = desired.normalize().mult(this.kp * error);

​

    // I: Integral term

    this.integral += error;

    let i = desired.normalize().mult(this.ki * this.integral);

​

    // D: Derivative term

    let d = desired.normalize().mult(this.kd * (error - this.prevError));

    this.prevError = error;

​

    this.acc = p5.Vector.add(p, p5.Vector.add(i, d));

    this.vel.add(this.acc);

    this.vel.limit(this.maxSpeed);

    this.pos.add(this.vel);

    this.acc.mult(0);

  }

​

  display() {

    fill(0, 255, 0);

    ellipse(this.pos.x, this.pos.y, 10, 10);

  }

}

​