Skip to content

Instantly share code, notes, and snippets.

@takatama
Created Dec 1, 2014
Embed
What would you like to do?
花火
http://thecodeplayer.com/walkthrough/canvas-fireworks-tutorial
https://developer.mozilla.org/samples/canvas-tutorial/6_1_canvas_composite.html
canvas {
display: block;
}
body {
background: #000;
margin: 0;
}
<canvas id="canvas">Canvas is not supported in this browser.</canvas>
(function() {
var hue = 120;
var particles = [];
var canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d'),
cw = window.innerWidth,
ch = window.innerHeight;
canvas.width = cw;
canvas.height = ch;
function random(min, max) {
return Math.random() * (max - min) + min;
}
function Particle(x, y) {
this.x = x; this.y = y;
this.coordinates = [];
this.coordinateCount = 3;
while (this.coordinateCount--) {
this.coordinates.push([this.x, this.y]);
}
this.angle = random(0, Math.PI * 2);
this.speed = random(1, 10);
this.friction = 0.95;
this.gravity = 1;
this.hue = random(hue - 20, hue + 20);
this.brightness = random(50, 80);
this.alpha = 1;
//残像を残したければ小さくする
this.decay = random(0.01, 0.02);
}
Particle.prototype.update = function(index) {
this.coordinates.pop();
this.coordinates.unshift([this.x, this.y]);
this.speed *= this.friction;
this.x += Math.cos(this.angle) * this.speed;
this.y += Math.sin(this.angle) * this.speed + this.gravity;
this.alpha -= this.decay;
if (this.alpha <= this.decay) {
particles.splice(index, 1);
}
};
Particle.prototype.draw = function() {
ctx.beginPath();
ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][1]);
ctx.lineTo(this.x, this.y);
ctx.strokeStyle = 'hsla(' + this.hue + ',100%,' + this.brightness + '%,' + this.alpha + ')';
ctx.stroke();
};
function createParticles(x, y) {
var particlesCount = parseInt(random(50, 200));
while (particlesCount--) {
particles.push(new Particle(x, y));
}
}
window.requestAnimFrame = (function() {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
function (callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
function createRandomParticles() {
var count = parseInt(random(1, 8));
while(count--) {
setTimeout(function() {
hue += 30;
createParticles(random(0, cw), random(0, ch));
}, parseInt(random(50, 300)));
}
}
var tick = 0, fireTick = 100;
function loop() {
requestAnimFrame(loop);
//軌跡はそのまま、透明度0.5で背景を黒で塗る
ctx.globalCompositeOperation = 'destination-out';
ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
ctx.fillRect(0, 0, cw, ch);
//光が重なったら明るくする
ctx.globalCompositeOperation = 'lighter';
var i = particles.length;
while(i--) {
particles[i].draw();
particles[i].update(i);
}
tick++;
if (tick > fireTick) {
createRandomParticles();
tick = parseInt(random(0, 50));
}
hue += 50;
}
canvas.addEventListener('mousedown', function(e) {
var x = e.pageX - canvas.offsetLeft;
var y = e.pageY - canvas.offsetTop;
createParticles(x, y);
});
window.onload = loop;
}());
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment