樱花雨的实现（附源码）

本文讲述如何在页面上实现樱花雨的效果：

效果图（这里没办法显示动态，具体动态自己复制代码去网页看）：

 





 


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HTML部分：




<body>
<div id="jsi-cherry-container" class="container"></div>
</body>




CSS部分：


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<style>
html, body{
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  overflow: hidden;
}
.container{
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  background-color: #000000;
}</style>


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js部分：


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<script src="js/jquery.min.js"></script>
<script>
    const CHERRY_BLOSSOM = function(renderer, isRandom){
    this.renderer = renderer;
    this.init(isRandom);
};
    const RENDERER = {
        INIT_CHERRY_BLOSSOM_COUNT: 30,
        MAX_ADDING_INTERVAL: 10,

        init: function () {
            this.setParameters();
            this.reconstructMethods();
            this.createCherries();
            this.render();
        },
        setParameters: function () {
            this.$container = $('#jsi-cherry-container');
            this.width = this.$container.width();
            this.height = this.$container.height();
            this.context = $('<canvas />').attr({
                width: this.width,
                height: this.height
            }).appendTo(this.$container).get(0).getContext('2d');
            this.cherries = [];
            this.maxAddingInterval = Math.round(this.MAX_ADDING_INTERVAL * 1000 / this.width);
            this.addingInterval = this.maxAddingInterval;
        },
        reconstructMethods: function () {
            this.render = this.render.bind(this);
        },
        createCherries: function () {
            let i = 0, length = Math.round(this.INIT_CHERRY_BLOSSOM_COUNT * this.width / 1000);
            for (; i < length; i++) {
                this.cherries.push(new CHERRY_BLOSSOM(this, true));
            }
        },
        render: function () {
            requestAnimationFrame(this.render);
            this.context.clearRect(0, 0, this.width, this.height);

            this.cherries.sort(function (cherry1, cherry2) {
                return cherry1.z - cherry2.z;
            });
            for (let i = this.cherries.length - 1; i >= 0; i--) {
                if (!this.cherries[i].render(this.context)) {
                    this.cherries.splice(i, 1);
                }
            }
            if (--this.addingInterval == 0) {
                this.addingInterval = this.maxAddingInterval;
                this.cherries.push(new CHERRY_BLOSSOM(this, false));
            }
        }
    };
    CHERRY_BLOSSOM.prototype = {
    FOCUS_POSITION : 300,
    FAR_LIMIT : 600,
    MAX_RIPPLE_COUNT : 100,
    RIPPLE_RADIUS : 100,
    SURFACE_RATE : 0.5,
    SINK_OFFSET : 20,
    
    init : function(isRandom){
        this.x = this.getRandomValue(-this.renderer.width, this.renderer.width);
        this.y = isRandom ? this.getRandomValue(0, this.renderer.height) : this.renderer.height * 1.5;
        this.z = this.getRandomValue(0, this.FAR_LIMIT);
        this.vx = this.getRandomValue(-2, 2);
        this.vy = -2;
        this.theta = this.getRandomValue(0, Math.PI * 2);
        this.phi = this.getRandomValue(0, Math.PI * 2);
        this.psi = 0;
        this.dpsi = this.getRandomValue(Math.PI / 600, Math.PI / 300);
        this.opacity = 0;
        this.endTheta = false;
        this.endPhi = false;
        this.rippleCount = 0;

        let axis = this.getAxis(),
            theta = this.theta + Math.ceil(-(this.y + this.renderer.height * this.SURFACE_RATE) / this.vy) * Math.PI / 500;
        theta %= Math.PI * 2;
        
        this.offsetY = 40 * ((theta <= Math.PI / 2 || theta >= Math.PI * 3 / 2) ? -1 : 1);
        this.thresholdY = this.renderer.height / 2 + this.renderer.height * this.SURFACE_RATE * axis.rate;
        this.entityColor = this.renderer.context.createRadialGradient(0, 40, 0, 0, 40, 80);
        this.entityColor.addColorStop(0, 'hsl(330, 70%, ' + 50 * (0.3 + axis.rate) + '%)');
        this.entityColor.addColorStop(0.05, 'hsl(330, 40%,' + 55 * (0.3 + axis.rate) + '%)');
        this.entityColor.addColorStop(1, 'hsl(330, 20%, ' + 70 * (0.3 + axis.rate) + '%)');
        this.shadowColor = this.renderer.context.createRadialGradient(0, 40, 0, 0, 40, 80);
        this.shadowColor.addColorStop(0, 'hsl(330, 40%, ' + 30 * (0.3 + axis.rate) + '%)');
        this.shadowColor.addColorStop(0.05, 'hsl(330, 40%,' + 30 * (0.3 + axis.rate) + '%)');
        this.shadowColor.addColorStop(1, 'hsl(330, 20%, ' + 40 * (0.3 + axis.rate) + '%)');
    },
    getRandomValue : function(min, max){
        return min + (max - min) * Math.random();
    },
    getAxis : function(){
        const rate = this.FOCUS_POSITION / (this.z + this.FOCUS_POSITION),
            x = this.renderer.width / 2 + this.x * rate,
            y = this.renderer.height / 2 - this.y * rate;
        return {rate : rate, x : x, y : y};
    },
    renderCherry : function(context, axis){
        context.beginPath();
        context.moveTo(0, 40);
        context.bezierCurveTo(-60, 20, -10, -60, 0, -20);
        context.bezierCurveTo(10, -60, 60, 20, 0, 40);
        context.fill();
        
        for(let i = -4; i < 4; i++){
            context.beginPath();
            context.moveTo(0, 40);
            context.quadraticCurveTo(i * 12, 10, i * 4, -24 + Math.abs(i) * 2);
            context.stroke();
        }
    },
    render : function(context){
        let end;
        let theta;
        const axis = this.getAxis();

        if(axis.y == this.thresholdY && this.rippleCount < this.MAX_RIPPLE_COUNT){
            context.save();
            context.lineWidth = 2;
            context.strokeStyle = 'hsla(0, 0%, 100%, ' + (this.MAX_RIPPLE_COUNT - this.rippleCount) / this.MAX_RIPPLE_COUNT + ')';
            context.translate(axis.x + this.offsetY * axis.rate * (this.theta <= Math.PI ? -1 : 1), axis.y);
            context.scale(1, 0.3);
            context.beginPath();
            context.arc(0, 0, this.rippleCount / this.MAX_RIPPLE_COUNT * this.RIPPLE_RADIUS * axis.rate, 0, Math.PI * 2, false);
            context.stroke();
            context.restore();
            this.rippleCount++;
        }
        if(axis.y < this.thresholdY || (!this.endTheta || !this.endPhi)){
            if(this.y <= 0){
                this.opacity = Math.min(this.opacity + 0.01, 1);
            }
            context.save();
            context.globalAlpha = this.opacity;
            context.fillStyle = this.shadowColor;
            context.strokeStyle = 'hsl(330, 30%,' + 40 * (0.3 + axis.rate) + '%)';
            context.translate(axis.x, Math.max(axis.y, this.thresholdY + this.thresholdY - axis.y));
            context.rotate(Math.PI - this.theta);
            context.scale(axis.rate * -Math.sin(this.phi), axis.rate);
            context.translate(0, this.offsetY);
            this.renderCherry(context, axis);
            context.restore();
        }
        context.save();
        context.fillStyle = this.entityColor;
        context.strokeStyle = 'hsl(330, 40%,' + 70 * (0.3 + axis.rate) + '%)';
        context.translate(axis.x, axis.y + Math.abs(this.SINK_OFFSET * Math.sin(this.psi) * axis.rate));
        context.rotate(this.theta);
        context.scale(axis.rate * Math.sin(this.phi), axis.rate);
        context.translate(0, this.offsetY);
        this.renderCherry(context, axis);
        context.restore();
        
        if(this.y <= -this.renderer.height / 4){
            if(!this.endTheta){
                for(; theta <= end; theta += Math.PI){
                    if(this.theta < theta && this.theta + Math.PI / 200 > theta){
                        this.theta = theta;
                        this.endTheta = true;
                        break;
                    }
                }
            }
            if(!this.endPhi){
                let phi = Math.PI / 8;
                end = Math.PI * 7 / 8;
                for(; phi <= end; phi += Math.PI * 3 / 4){
                    if(this.phi < phi && this.phi + Math.PI / 200 > phi){
                        this.phi = Math.PI / 8;
                        this.endPhi = true;
                        break;
                    }
                }
            }
        }
        if(!this.endTheta){
            if(axis.y == this.thresholdY){
                this.theta += Math.PI / 200 * ((this.theta < Math.PI / 2 || (this.theta >= Math.PI && this.theta < Math.PI * 3 / 2)) ? 1 : -1);
            }else{
                this.theta += Math.PI / 500;
            }
            this.theta %= Math.PI * 2;
        }
        if(this.endPhi){
            if(this.rippleCount == this.MAX_RIPPLE_COUNT){
                this.psi += this.dpsi;
                this.psi %= Math.PI * 2;
            }
        }else{
            this.phi += Math.PI / ((axis.y == this.thresholdY) ? 200 : 500);
            this.phi %= Math.PI;
        }
        if(this.y <= -this.renderer.height * this.SURFACE_RATE){
            this.x += 2;
            this.y = -this.renderer.height * this.SURFACE_RATE;
        }else{
            this.x += this.vx;
            this.y += this.vy;
        }
        return this.z > -this.FOCUS_POSITION && this.z < this.FAR_LIMIT && this.x < this.renderer.width * 1.5;
    }
};
$(function(){
    RENDERER.init();
});</script>


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