// Daniel Shiffman

// http://natureofcode.com

​

// Simple Particle System

​

// A simple Particle class

​

var Particle = function(position, img) {

  this.acceleration = createVector(0, 0.05);

  this.velocity = createVector(random(-1, 1), random(-1, 0));

  this.position = position.copy();

  this.lifespan = 255.0;

    this.image = img;

  this.run = function() {

    this.update();

    this.display();

  };

​

  // Method to update position

  this.update = function(){

    this.velocity.add(this.acceleration);

    this.position.add(this.velocity);

    this.lifespan -= 2;

  };

​

  // Method to apply a force vector to the Particle object

  // Note we are ignoring "mass" here

  this.applyForce = function(f) {

    this.acceleration.add(f);

  }  

  // Method to display

  this.display = function() {

        //imageMode(CENTER);

    //tint(255,lifespan);

    //image(img,loc.x,loc.y);

    // Drawing a circle instead

    fill(255,this.lifespan);

    noStroke();

    ellipse(this.position.x,this.position.y,this.image.width,this.image.height);

  };

​

  // Is the particle still useful?

  this.isDead = function(){

    if (this.lifespan < 0.0) {

        return true;

    } else {

      return false;

    }

  };

};