Example tutorial HTML5 Canvas super cool fireworks bloom animation implementation code

This is a cool HTML5 Canvas animation. It will simulate the animated special effects of fireworks blooming in our real life. The effect is very realistic, but after all, it is a computer simulation. Even if you take your girlfriend to watch it, the effect is still a bit poor. ,hehe. One thing that is outstanding about this HTML5 Canvas animation is its performance. There is basically no lag on Chrome, even if you set off a lot of fireworks.

Let’s briefly analyze the process and code to implement this HTML5 firework special effect. It is mainly composed of HTML code, CSS code and Javascript code. Of course, the javascript code is the most important.

　HTML code:

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<div id=”gui”>div>
<div id=”canvas-container”> <div id=”mountains2″>div>
<div id=”mountains1″ >div><div id=”skyline”>div> div>

The structure of HTML is very simple, that is, a canvas container is constructed, and we will use JS to generate a Canvas object in this container. You will know it by looking at the final JS code.

　CSS code:

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#canvas-container { background: #000 url(bg.jpg); height: 400px; left: 50%; margin: -200px 0 0 -300px; position: absolute; top: 50%; width: 600px; z-index: 2;
} canvas { cursor: crosshair; display: block; position: relative; z-index: 3;
} canvas:active { cursor: crosshair;
} #skyline { background: url(skyline.png) repeat-x 50% 0; bottombottom: 0; height: 135px; left: 0; position: absolute; width: 100%; z-index: 1;
} #mountains1 { background: url(mountains1.png) repeat-x 40% 0; bottombottom: 0; height: 200px; left: 0; position: absolute; width: 100%; z-index: 1;
} #mountains2 { background: url(mountains2.png) repeat-x 30% 0; bottombottom: 0; height: 250px; left: 0; position: absolute; width: 100%; z-index: 1;
} #gui { rightright: 0; position: fixed; top: 0; z-index: 3;
}

The CSS code is nothing special, it mainly defines the background color and border.

Next is the most important Javascript code.

　Javascript code:

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self.init = function(){
self.dt = 0;
self.oldTime = Date.now();
self.canvas = document.createElement('canvas');
self.canvasContainer = $('#canvas-container'); var canvasContainerDisabled = document.getElementById('canvas-container');
self.canvas.onselectstart = function() { return false;
};
self.canvas.width = self.cw = 600;
self.canvas.height = self.ch = 400;
self.particles = [];
self.partCount = 30;
self.fireworks = [];
self.mx = self.cw/2;
self.my = self.ch/2;
self.currentHue = 170;
self.partSpeed = 5;
self.partSpeedVariance = 10;
self.partWind = 50;
self.partFriction = 5;
self.partGravity = 1;
self.hueMin = 150;
self.hueMax = 200;
self.fworkSpeed = 2;
self.fworkAccel = 4;
self.hueVariance = 30;
self.flickerDensity = 20;
self.showShockwave = false;
self.showTarget = true;
self.clearAlpha = 25;
self.canvasContainer.append(self.canvas);
self.ctx = self.canvas.getContext('2d');
self.ctx.lineCap = 'round';
self.ctx.lineJoin = 'round';
self.lineWidth = 1;
self.bindEvents();
self.canvasLoop();
self.canvas.onselectstart = function() { return false;
};
};

This JS code mainly constructs a Canvas object in the canvas container, and initializes the appearance and animation properties of the canvas object.

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var Particle = function(x, y, hue){ this.x = x; this.y = y; this.coordLast = [
{x: x, y: y},
{x: x, y: y},
{x: x, y: y}
]; this.angle = rand(0, 360); this.speed = rand(((self.partSpeed - self.partSpeedVariance) <= 0) ? 1 : self.partSpeed - self.partSpeedVariance, (self.partSpeed self.partSpeedVariance)); this.friction = 1 - self.partFriction/100; this.gravity = self.partGravity/2; this.hue = rand(hue-self.hueVariance, hue self.hueVariance); this.brightness = rand(50, 80); this.alpha = rand(40,100)/100; this.decay = rand(10, 50)/1000; this.wind = (rand(0, self.partWind) - (self.partWind/2))/25; this.lineWidth = self.lineWidth;
};
Particle.prototype.update = function(index){ var radians = this.angle * Math.PI / 180; var vx = Math.cos(radians) * this.speed; var vy = Math.sin(radians) * this.speed this.gravity; this.speed *= this.friction; this.coordLast[2].x = this.coordLast[1].x; this.coordLast[2].y = this.coordLast[1].y; this.coordLast[1].x = this.coordLast[0].x; this.coordLast[1].y = this.coordLast[0].y; this.coordLast[0].x = this.x; this.coordLast[0].y = this.y; this.x = vx * self.dt; this.y = vy * self.dt; this.angle = this.wind; this.alpha -= this.decay; if(!hitTest(0,0,self.cw,self.ch,this.x-this.radius, this.y-this.radius, this.radius*2, this.radius*2) || this.alpha < .05){
self.particles.splice(index, 1);
}
};
Particle.prototype.draw = function(){ var coordRand = (rand(1,3)-1);
self.ctx.beginPath();
self.ctx.moveTo(Math.round(this.coordLast[coordRand].x), Math.round(this.coordLast[coordRand].y));
self.ctx.lineTo(Math.round(this.x), Math.round(this.y));
self.ctx.closePath();
self.ctx.strokeStyle = 'hsla(' this.hue ', 100%, ' this.brightness '%, ' this.alpha ')';
self.ctx.stroke(); if(self.flickerDensity > 0){ var inverseDensity = 50 - self.flickerDensity; if(rand(0, inverseDensity) === inverseDensity){
self.ctx.beginPath();
self.ctx.arc(Math.round(this.x), Math.round(this.y), rand(this.lineWidth,this.lineWidth 3)/2, 0, Math.PI*2, false) self.ctx.closePath(); var randAlpha = rand(50,100)/100;
self.ctx.fillStyle = 'hsla(' this.hue ', 100%, ' this.brightness '%, ' randAlpha ')';
self.ctx.fill();
}
}
};

　　这段JS代码的功能是实现烟花爆炸后的小颗粒的绘制，从draw方法中可以看出，创建几个随机点，烟花颗粒即可在这个范围的随机点中散落。

JavaScript Code复制内容到剪贴板

var Firework = function(startX, startY, targetX, targetY){ this.x = startX; this.y = startY; this.startX = startX; this.startY = startY; this.hitX = false; this.hitY = false; this.coordLast = [
{x: startX, y: startY},
{x: startX, y: startY},
{x: startX, y: startY}
]; this.targetX = targetX; this.targetY = targetY; this.speed = self.fworkSpeed; this.angle = Math.atan2(targetY - startY, targetX - startX); this.shockwaveAngle = Math.atan2(targetY - startY, targetX - startX) (90*(Math.PI/180)); this.acceleration = self.fworkAccel/100; this.hue = self.currentHue; this.brightness = rand(50, 80); this.alpha = rand(50,100)/100; this.lineWidth = self.lineWidth; this.targetRadius = 1;
};
Firework.prototype.update = function(index){
self.ctx.lineWidth = this.lineWidth;
vx = Math.cos(this.angle) * this.speed,
vy = Math.sin(this.angle) * this.speed; this.speed *= 1 this.acceleration; this.coordLast[2].x = this.coordLast[1].x; this.coordLast[2].y = this.coordLast[1].y; this.coordLast[1].x = this.coordLast[0].x; this.coordLast[1].y = this.coordLast[0].y; this.coordLast[0].x = this.x; this.coordLast[0].y = this.y; if(self.showTarget){ if(this.targetRadius < 8){ this.targetRadius = .25 * self.dt;
} else { this.targetRadius = 1 * self.dt;
}
} if(this.startX >= this.targetX){ if(this.x vx <= this.targetX){ this.x = this.targetX; this.hitX = true;
} else { this.x = vx * self.dt;
}
} else { if(this.x vx >= this.targetX){ this.x = this.targetX; this.hitX = true;
} else { this.x = vx * self.dt;
}
} if(this.startY >= this.targetY){ if(this.y vy <= this.targetY){ this.y = this.targetY; this.hitY = true;
} else { this.y = vy * self.dt;
}
} else { if(this.y vy >= this.targetY){ this.y = this.targetY; this.hitY = true;
} else { this.y = vy * self.dt;
}
} if(this.hitX && this.hitY){ var randExplosion = rand(0, 9);
self.createParticles(this.targetX, this.targetY, this.hue);
self.fireworks.splice(index, 1);
}
};
Firework.prototype.draw = function(){
self.ctx.lineWidth = this.lineWidth; var coordRand = (rand(1,3)-1);
self.ctx.beginPath();
self.ctx.moveTo(Math.round(this.coordLast[coordRand].x), Math.round(this.coordLast[coordRand].y));
self.ctx.lineTo(Math.round(this.x), Math.round(this.y));
self.ctx.closePath();
self.ctx.strokeStyle = 'hsla(' this.hue ', 100%, ' this.brightness '%, ' this.alpha ')';
self.ctx.stroke(); if(self.showTarget){
self.ctx.save();
self.ctx.beginPath();
self.ctx.arc(Math.round(this.targetX), Math.round(this.targetY), this.targetRadius, 0, Math.PI*2, false)
self.ctx.closePath();
self.ctx.lineWidth = 1;
self.ctx.stroke();
self.ctx.restore();
} if(self.showShockwave){
self.ctx.save();
self.ctx.translate(Math.round(this.x), Math.round(this.y));
self.ctx.rotate(this.shockwaveAngle);
self.ctx.beginPath();
self.ctx.arc(0, 0, 1*(this.speed/5), 0, Math.PI, true);
self.ctx.strokeStyle = 'hsla(' this.hue ', 100%, ' this.brightness '%, ' rand(25, 60)/100 ')';
self.ctx.lineWidth = this.lineWidth;
self.ctx.stroke();
self.ctx.restore();
}
};