In this simple program, we animate an ellipse to always chase a point defined by the mouse. The ellipse only ever moves a percentage of the distance between it and the target destination in each step. The p5.Vector object is used to handle the coordinates and the simple math operations.

Exercise

Add an additional ellipse that follows the mouse at a slower rate than the first ellipse.
Modify the code so that the ellipse always follows the mouse position.
Replace with the ellipse with another shape (like a triangle or even a car) , and keep it pointed towards the mouse.

var pos;
var targetPos;
var mousePos;

function setup() {
  createCanvas(1000, 600);
  fill(0);
  pos = createVector(0, 0);
  targetPos = createVector(0, 0);
  mousePos = createVector(width/2, height/2);
}

function draw() {
  background(255);
  targetPos.set(mousePos); 
  targetPos.sub(pos);  // find the vector between mouse position and ellipse position
  targetPos.mult(0.2); // each step in the animation will move this percentage of the distance to the target position
  pos.add(targetPos);
  ellipse(pos.x, pos.y, 60, 60);
}

function mousePressed() {
  mousePos.set(mouseX, mouseY);
}

Exercise Solution Using Arrays

var pos = [];
var targetPos = [];
var mousePos = [];
var arrayLength = 5;

function setup() {
  createCanvas(1000, 600);
  fill(0);
  for (var i = 0; i< arrayLength; i++) { 
    pos[i] = createVector(0, 0);
    targetPos[i] = createVector(0, 0);
  }
   mousePos = createVector(width/2, height/2);
}

function draw() {
   mousePos.set(mouseX, mouseY);
   background(255);
  
  for (var i = 0; i < pos.length; i++) { 
        targetPos[i].set(mousePos); 
        targetPos[i].sub(pos[i]);  // find the vector between mouse position and ellipse position
        targetPos[i].mult((i*0.02) + 0.05); // each step in the animation will move this percentage of the distance to the target position
        pos[i].add(targetPos[i]);
        fill(125,255,23);
        ellipse(pos[i].x, pos[i].y, 60, 60);
    }
}

Exercise Solution Using Arrays and Objects

let shape = [];
var arrayLength = 60;


function setup() {
  createCanvas(1000, 600);
  fill(0);

  for (var i= 0; i < arrayLength; i++) {
    shape[i] = new myShape((i*0.02) + 0.02);
  }
}

function draw() {
  background(255);
  for (var i= 0; i < shape.length; i++) {
    shape[i].update();
  }
}

class myShape {
  
  constructor(_speed) {
   this.pos = createVector(0,0);
   this.targetPos = createVector(0,0);
   this.mousePos = createVector(width/2, height/2);
   this.speed = _speed;
  }
  

  update() {
    this.mousePos.set(mouseX, mouseY);
    this.targetPos.set(this.mousePos); 
    this.targetPos.sub(this.pos);  // find the vector between mouse position and ellipse position
    this.targetPos.mult(this.speed); // each step in the animation will move this percentage of the distance to the target position
    this.pos.add(this.targetPos);
    
    pushMatrix();
    translate(this.pos.x, this.pos.y);
    rotate(calcAngle(this.pos, this.mousePos));
    triangle(0,0,-5,20,5,20);
    popMatrix();
  }

  calcAngle(p1, p2)
  {
    return -atan2(p1.x - p2.x,p1.y - p2.y);
  }
}

Programming

p5.js Animation Exercise 1

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Exercise

Exercise Solution Using Arrays

Exercise Solution Using Arrays and Objects

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