<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>canvas烟花</title>
<style>
canvas {
background-color:#000000;
position:absolute;
top:0px;
left:0px;
}
</style>
</head>
<body>
<canvas id="screen"></canvas>
<script>
// Code by Matheus Lin
// While developing a version of "Chain Reaction", I ended up on
// those "fireworks-like" things. I leave it to you here.
// Chain Reaction coming up next!
// Configs
var screenWidth = window.innerWidth;
var screenHeight = window.innerHeight;
var minVx = -10;
var deltaVx = 20;
var minVy = 25
var deltaVy = 15;
var minParticleV = 5;
var deltaParticleV = 5;
var gravity = 1;
var explosionRadius = 200;
var bombRadius = 10;
var explodingDuration = 100;
var explosionDividerFactor = 10; // I couldn't find a better name. Got any?
var nBombs = 1; // initial
var percentChanceNewBomb = 5;
// Color utils forked from http://andreasstorm.com/
// (or someone who forked from there)
function Color(min) {
min = min || 0;
this.r = colorValue(min);
this.g = colorValue(min);
this.b = colorValue(min);
this.style = createColorStyle(this.r, this.g, this.b);
};
function colorValue(min) {
return Math.floor(Math.random() * 255 + min);
}
function createColorStyle(r,g,b) {
return 'rgba(' + r + ',' + g + ',' + b + ', 0.8)';
}
// A Bomb. Or firework.
function Bomb(){
var self = this;
self.radius = bombRadius;
self.previousRadius = bombRadius;
self.explodingDuration = explodingDuration;
self.hasExploded = false;
self.alive = true;
self.color = new Color();
self.px = (window.innerWidth / 4) + (Math.random() * window.innerWidth / 2);
self.py = window.innerHeight;
self.vx = minVx + Math.random() * deltaVx;
self.vy = (minVy + Math.random() * deltaVy) * -1; // because y grows downwards
self.duration =
self.update = function(particlesVector){
if(self.hasExploded){
var deltaRadius = explosionRadius - self.radius;
self.previousRadius = self.radius;
self.radius += deltaRadius / explosionDividerFactor;
self.explodingDuration--;
if(self.explodingDuration == 0){
self.alive = false;
}
}
else{
self.vx += 0;
self.vy += gravity;
if(self.vy >= 0){ // invertion point
self.explode(particlesVector);
}
self.px += self.vx;
self.py += self.vy;
}
};
self.draw = function(ctx){
ctx.beginPath();
ctx.arc(self.px, self.py, self.previousRadius, 0, Math.PI * 2, false);
if(self.hasExploded){
}
else{
ctx.fillStyle = self.color.style;
ctx.lineWidth = 1;
ctx.fill();
}
};
self.explode = function(particlesVector){
self.hasExploded = true;
var e = 3 + Math.floor(Math.random() * 3);
for(var j = 0; j < e; j++){
var n = 10 + Math.floor(Math.random() * 21); // 10 - 30
var speed = minParticleV + Math.random() * deltaParticleV;
var deltaAngle = 2 * Math.PI / n;
var initialAngle = Math.random() * deltaAngle;
for(var i = 0; i < n; i++){
particlesVector.push(new Particle(self, i * deltaAngle + initialAngle, speed));
}
}
};
}
function Particle(parent, angle, speed){
var self = this;
self.px = parent.px;
self.py = parent.py;
self.vx = Math.cos(angle) * speed;
self.vy = Math.sin(angle) * speed;
self.color = parent.color;
self.duration = 40 + Math.floor(Math.random()*20);
self.alive = true;
self.update = function(){
self.vx += 0;
self.vy += gravity / 10;
self.px += self.vx;
self.py += self.vy;
self.radius = 3;
self.duration--;
if(self.duration <= 0){
self.alive = false;
}
};
self.draw = function(ctx){
ctx.beginPath();
ctx.arc(self.px, self.py, self.radius, 0, Math.PI * 2, false);
ctx.fillStyle = self.color.style;
ctx.lineWidth = 1;
ctx.fill();
};
}
function Controller(){
var self = this;
self.canvas = document.getElementById("screen");
self.canvas.width = screenWidth;
self.canvas.height = screenHeight;
self.ctx = self.canvas.getContext('2d');
function setSpeedParams(){
var heightReached = 0;
var vy = 0;
while(heightReached < screenHeight && vy >= 0){
vy += gravity;
heightReached += vy;
}
minVy = vy / 2;
deltaVy = vy - minVy;
vx = (1 / 4) * screenWidth / (vy / 2);
minVx = -vx;
deltaVx = 2*vx;
};
self.resize = function(){
screenWidth = window.innerWidth;
screenHeight = window.innerHeight;
self.canvas.width = screenWidth;
self.canvas.height = screenHeight;
setSpeedParams();
};
self.resize();
window.onresize = self.resize;
self.init = function(){
self.readyBombs = [];
self.explodedBombs = [];
self.particles = [];
for(var i = 0; i < nBombs; i++){
self.readyBombs.push(new Bomb());
}
}
self.update = function(){
var aliveBombs = [];
while(self.explodedBombs.length > 0){
var bomb = self.explodedBombs.shift();
bomb.update();
if(bomb.alive){
aliveBombs.push(bomb);
}
}
self.explodedBombs = aliveBombs;
var notExplodedBombs = [];
while(self.readyBombs.length > 0){
var bomb = self.readyBombs.shift();
bomb.update(self.particles);
if(bomb.hasExploded){
self.explodedBombs.push(bomb);
}
else{
notExplodedBombs.push(bomb);
}
}
self.readyBombs = notExplodedBombs;
var aliveParticles = [];
while(self.particles.length > 0){
var particle = self.particles.shift();
particle.update();
if(particle.alive){
aliveParticles.push(particle);
}
}
self.particles = aliveParticles;
}
self.draw = function(){
self.ctx.beginPath();
self.ctx.fillStyle='rgba(0, 0, 0, 0.1)'; // Ghostly effect
self.ctx.fillRect(0, 0, self.canvas.width, self.canvas.height);
for(var i = 0; i < self.readyBombs.length; i++){
self.readyBombs[i].draw(self.ctx);
}
for(var i = 0; i < self.explodedBombs.length; i++){
self.explodedBombs[i].draw(self.ctx);
}
for(var i = 0; i < self.particles.length; i++){
self.particles[i].draw(self.ctx);
}
}
self.animation = function(){
self.update();
self.draw();
if(Math.random() * 100 < percentChanceNewBomb) {
self.readyBombs.push(new Bomb());
}
requestAnimationFrame(self.animation);
}
}
var controller = new Controller();
controller.init();
requestAnimationFrame(controller.animation);</script>
</body>
</html>
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