September 29, 2016

example processing creating-classes animation

This program creates a Flyer class to encapsulate all of the logic for creating a “bug” :honeybee: that follows the mouse around using a heading angle and a speed. This provides more realistic movement, but it lets us keep our draw() function nice and simple.

Flyer[] flyers = new Flyer[5];

void setup(){
  size(200, 200);

  for(int i = 0; i < flyers.length; i++){
    flyers[i] = new Flyer();

void draw(){

  for(int i = 0; i < flyers.length; i++){

class Flyer{

  float x = random(width);
  float y = random(height);
  float heading = random(TWO_PI);
  float speed = random(1, 3);  
  float radius = random(5, 20);

  void step(){

    float angleToMouse = atan2(mouseY-y, mouseX-x);

    //prevent case where heading is 350 and angleToMouse is 10
    if(heading-angleToMouse > PI){
      angleToMouse += TWO_PI;
    else if(angleToMouse-heading > PI){
      angleToMouse -= TWO_PI;

    //turn towards mouse
    if(heading < angleToMouse){

    //move in direction
    x += cos(heading)*speed;
    y += sin(heading)*speed;

    //wrap around edges
    if(x < 0){
      x = width;
    if(x > width){
      x = 0;

    if(y < 0){
      y = height;
    if(y > height){
      y = 0;


  void draw(){
    ellipse(x, y, radius, radius);


five Flyers

Code Editor

See the Pen by Happy Coding (@KevinWorkman) on CodePen.

If this seems complicated, think about it this way: when using a class, we only need to worry about the behavior of a single Flyer instance (in other words, we only need to know how a single “bug” behaves). Then when we get that single Flyer working, we can use an array or an ArrayList to add as many Flyer instances as we want!

100 Flyers

Tweak Ideas

  • Give each Flyer a random color.
  • Move the call to background() to the setup() function to show trails.
  • Make them run away from the mouse instead of chase it.

Creating Classes Examples


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