[Canvas]更多的球

欲观看动态效果请点此下载代码并用Chrome或者Firefox打开。
图例：
代码：
<!DOCTYPE html>
<html lang="utf-8">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<head>
     <title>更多碰撞球 19.3.4 8:53 by:逆火狂飙 horn19782016@163.com</title>

     <style>
     #canvas{
        background:#ffffff;
        cursor:pointer;
        margin-left:10px;
        margin-top:10px;
        -webkit-box-shadow:3px 3px 6px rgba(0,0,0,0.5);
        -moz-box-shadow:3px 3px 6px rgba(0,0,0,0.5);
        box-shadow:3px 3px 6px rgba(0,0,0,0.5);
     }

     #controls{
        margin-top:10px;
        margin-left:15px;
     }
     </style>

    </head>

     <body onload="init()">
        <div id="controls">
            <input id='animateBtn' type='button' value='运动'/>
        </div>

        <canvas id="canvas" width="750px" height="500px" >
            出现文字表示你的浏览器不支持HTML5
        </canvas>
     </body>
</html>
<script type="text/javascript">
<!--
var paused=true;
animateBtn.onclick=function(e){
    paused=! paused;

    if(paused){
        animateBtn.value="运动";
    }else{

        animateBtn.value="暂停";
        window.requestAnimationFrame(animate);
    }
}
//生成从minNum到maxNum的随机数
function randomNum(minNum,maxNum){
    switch(arguments.length){
        case 1:
            return parseInt(Math.random()*minNum+1,10);
        break;
        case 2:
            return parseInt(Math.random()*(maxNum-minNum+1)+minNum,10);
        break;
            default:
                return 0;
            break;
    }
}

var ctx;// 绘图环境
var balls=[];// 球数组
function init(){

    var canvas=document.getElementById('canvas');
    canvas.width=750;
    canvas.height=500;
    ctx=canvas.getContext('2d');

    for(var i=0;i<500;i++){
        var ball={};
        ball.x=randomNum(0,canvas.width);
        ball.y=randomNum(0,canvas.height);

        ball.vx=randomNum(-10,10);
        ball.vy=randomNum(-10,10);
        ball.radius=25;
        var r=randomNum(0,255);
        var g=randomNum(0,255);
        var b=randomNum(0,255);
        ball.innerColor='rgba('+r+','+g+','+b+',1)';
        ball.middleColor='rgba('+r+','+g+','+b+',0.5)';
        ball.outerColor='rgba('+r+','+g+','+b+',0.3)';
        ball.strokeStyle='rgba('+r+','+g+','+b+')';

        balls.push(ball);
    }
};

function update(){
    for(var i=0;i<balls.length;i++){
        var ball=balls[i];

        // 与左右墙壁的碰撞检测
        if(ball.x+ball.vx+ball.radius>ctx.canvas.width || ball.x+ball.vx-ball.radius<0){
            ball.vx=-ball.vx;
        }

        // 与上下墙壁的碰撞检测
        if(ball.y+ball.vy+ball.radius>ctx.canvas.height || ball.y+ball.vy-ball.radius<0){
            ball.vy=-ball.vy;
        }

        // 小球之前的碰撞检测
        for(var j=0;j<balls.length;j++){
            if(i!=j){
                var other=balls[j];

                var distance=Math.sqrt( Math.pow((ball.x+ball.vx-other.x-other.vx),2)+Math.pow((ball.y+ball.vy-other.y-other.vy),2));

                if(distance<ball.radius+other.radius){
                    // 如果两个碰撞小球的质量相等，联立动量守恒和能量守恒方程时可解得：两个小球碰撞后交换速度。
                    var x=ball.vx;
                    ball.vx=other.vx;
                    other.vx=x;

                    var y=ball.vy;
                    ball.vy=other.vy;
                    other.vy=y;
                }
            }
        }

        ball.x+=ball.vx;
        ball.y+=ball.vy;
    }
}

function draw(){
    ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height);

    for(var i=0;i<balls.length;i++){
        var ball=balls[i];

        gradient=ctx.createRadialGradient(ball.x,ball.y,0,ball.x,ball.y,ball.radius);
        gradient.addColorStop(0.3,ball.innerColor);
        gradient.addColorStop(0.5,ball.middleColor);
        gradient.addColorStop(1.0,ball.outerColor);

        ctx.save();
        ctx.beginPath();
        ctx.arc(ball.x,ball.y,ball.radius,0,Math.PI*2,false);
        ctx.fillStyle=gradient;
        ctx.strokeStyle=ball.strokeStyle;
        ctx.fill();
        ctx.stroke();
        ctx.restore();
    }
}

function animate(){
    if(!paused){

        update();
        draw();

        setTimeout( function(){
            window.requestAnimationFrame(animate); /// 让浏览器自行决定帧速率
        }, 0.10 * 1000 );// 延时执行
    }
}
//-->
</script>
2019年3月4日09点12分
巴特西

[Canvas]更多的球

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