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particles.js
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particles.js
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function Explosion(canvasId, startX, startY)
{
this.startX = startX;
this.startY = startY;
this.color = new Array(255, 144, 0);
this.size = 1;
this.gravity = 0.5;
this.friction = .9;
this.particles = new Array();
this.maxParticles = 200;
this.maxBlastParticles = 80;
this.canvasContext = document.getElementById(canvasId).getContext("2d")
this.createParticle = function()
{
if(this.particles.length > this.maxParticles)
{
this.particles[0].lifeSpan = 1;
this.particles[0].velocityX = (Math.random() * 40) - 20;
this.particles[0].velocityY = (Math.random() * 30) - 15;
this.particles[0].x = this.startX;
this.particles[0].y = this.startY;
this.particles.push(this.particles.shift());
}
else
{
var particle = new Particle();
particle.x = this.startX;
particle.y = this.startY;
particle.velocityX = (Math.random() * 45) - 22;
particle.velocityY = (Math.random() * 5);
this.particles.push(particle);
}
}
this.step = function()
{
for(i = 0; i < this.particles.length; i++)
{
this.particles[i].x -= this.particles[i].velocityX;
this.particles[i].y -= this.particles[i].velocityY;
this.particles[i].velocityX *= this.friction;
this.particles[i].velocityY *= this.friction;
this.particles[i].velocityY -= this.gravity;
this.particles[i].lifeSpan -= .02;
if(this.particles[i].lifeSpan < 0)
{
this.particles.splice(i, 1);
}
}
}
this.draw = function()
{
this.canvasContext.clearRect(0, 0, 800, 600);
for(i = 0; i < this.particles.length; i++)
{
this.canvasContext.fillStyle = 'rgba('+this.color[0]+','+this.color[1]+','+this.color[2]+','+this.particles[i].lifeSpan+')';
this.canvasContext.beginPath();
this.canvasContext.arc(this.particles[i].x, this.particles[i].y, this.size*this.particles[i].lifeSpan, 0, Math.PI*2, true);
this.canvasContext.fill();
}
}
}
function Particle()
{
this.x = 0;
this.y = 0;
this.velocityY = 0;
this.velocityX = 0;
this.lifeSpan = 3;
}
//Globals
var explosion;
var maxBlastParticles = 10;
function createExplosion()
{
explosion = new Explosion('explosion-canvas', 0, 0);
//global loop
setInterval('stepExplosion()', 10);
var canvas = document.getElementById('explosion-canvas');
canvas.addEventListener('click', fireParticle, false);
}
function onWindowMouseClick(e)
{
if(e.offsetX) {
mouseX = e.offsetX;
mouseY = e.offsetY;
}
else if(e.layerX) {
mouseX = e.layerX;
mouseY = e.layerY;
}
}
function stepExplosion()
{
explosion.step();
explosion.draw();
}
function fireParticle(e)
{
if(e.offsetX) {
explosion.startX = e.offsetX;
explosion.startY = e.offsetY;
}
else if(e.layerX) {
explosion.startX = e.layerX;
explosion.startY = e.layerY;
}
for(i = 0; i < maxBlastParticles; i++) {
explosion.createParticle();
}
}