​

let leader; //Vector

let leadSpd; //Vector

let follower = []; //Vector

let followerSpd = []; //vector

let circRed = 50;

let circGreen = 50;

let circBlue = 50;

​

​

​

let springing = 0.01;

let damping = 0.1;

​

function setup() {

  createCanvas(600, 600); // size()

  bounds = createVector(400, 400);

  strokeWeight(3);

​

  leader = createVector();

  console.log(leader);

  leadSpd = createVector(random(-1.5, 1.5), random(-1.5, 1.5));

​

​

  follower[0] = createVector();

  followerSpd[0] = createVector(); 

  follower[1] = createVector(-200,200);

  followerSpd[1] = createVector(); 

  follower[2] = createVector(200,200);

  followerSpd[2] = createVector();

  follower[3] = createVector();

  followerSpd[3] = createVector(); 

}

​

function draw() {

  background(255, 255, 255, 20);

  translate(width / 2, height / 2);

  drawBounds();

  makeleader();

  follow();

  render();

  checkEdge();

}

​

function drawBounds() {

  noFill();

  stroke(0);

  rect(-bounds.x / 2, -bounds.y / 2, bounds.x, bounds.y);

}

​

function makeleader() {

  leadSpd.add(createVector(random(-0.2, 0.2), random(-0.2, 0.2)));

  leader.add(leadSpd); // euler integration

}

​

function follow() {

  //move center point

  let deltaX = [];

  let deltaY=[];

  for (let i = 0; i < follower.length; i++) {

     deltaX[i] = leader.x - follower[i].x;

     deltaY[i] = leader.y - follower[i].y;

​

    // create springing effect

    deltaX[i] *= springing;

    deltaY[i] *= springing;

    followerSpd[i].x += deltaX[i];

    followerSpd[i].y += deltaY[i];

​

    // move predator's center Euler

    follower[i].x += followerSpd[i].x;

    follower[i].y += followerSpd[i].y;

​

    // slow down springing

   followerSpd[i].x *= damping;

   followerSpd[i].y *= damping;

  }

}

​

function render() {

  stroke(150);

  noStroke();

  ellipse(leader.x, leader.y, 25, 25);

  fill(15, 170, 255);

  for (let i = 0; i < follower.length; i++) {

    ellipse(follower[i].x, follower[i].y, 25, 18);

  }

}

​

function checkEdge() {

  //leader

  if (leader.x > bounds.x / 2) {

    leader.x = bounds.x / 2;

    leadSpd.x *= -1;

  } else if (leader.x < -bounds.x / 2) {

    leader.x = -bounds.x / 2;

    leadSpd.x *= -1;

  }

​

  if (leader.y > bounds.y / 2) {

    leader.y = bounds.y / 2;

    leadSpd.y *= -1;

  } else if (leader.y < -bounds.y / 2) {

    leader.y = -bounds.y / 2;

    leadSpd.y *= -1;

  }

​

  //follower

  if (follower.x > bounds.x / 2) {

    follower.x = bounds.x / 2;

    followerSpd.x *= -1;

  } else if (follower.x < -bounds.x / 2) {

    follower.x = -bounds.x / 2;

    followerSpd.x *= -1;

  }

​

  if (follower.y > bounds.y / 2) {

    follower.y = bounds.y / 2;

    followerSpd.y *= -1;

  } else if (follower.y < -bounds.y / 2) {

    follower.y = -bounds.y / 2;

    followerSpd.y *= -1;

  }

}

​