html5 canvas实例碰撞检测撞球示例

2024-09-05 12:18:49

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html5 canvas撞球动画示例碰撞检测，演示过程中，在页面上始终显示FPS AVG: 84.61 CUR: 83.42 number:1等信息，可定义缓冲和不缓冲，点击“buffer”后可看到，很多小球在无规则运动，撞到边缘会自动弹回，对canvas的理解有帮助。

<!DOCTYPE HTML><html><title>html5 canvas撞球实例 碰撞检测</title><body><div style="width:400px;margin:0 auto"><canvas id="main" style="background-color:green;width:400px;height:400px"></canvas><div id="fps"></div><input type="button" value="stop" onclick="cancel()"/><input type="button" value="noBuffer" onclick="addCreatures(10)"/><input type="button" value="Buffer" id="buf"/></div></body><script>var ctx;var width;var height;var delta;var lastTime;var frames;var totalTime;var updateTime;var updateFrames;var creats = new Array();var id;var nobufferArr = [],bufferArr = [];var manipulate = {    MAX : 300,    head : 0,    tail : 0,    history : [],    id : -1,    clickHander : function(e){        this.history[this.head] = 1;        this.head = (this.head + 1 + this.MAX) % this.MAX;    },    init : function(){        for(var i = 0; i < 300; i++){            this.history[i] = 0;        }        that = this;        this.id = setInterval(function(){           var len = (that.head - that.tail + that.MAX) % that.MAX;            if(len > 0){                                for(var i = 0; i<len; i++){                    that.tail = that.tail % that.MAX;                    if(that.history[that.tail]==1){                         addCreatures(10);                         that.history[that.tail]=0;                         if(this.head>300) clearInterval(this.id);                    }                    that.tail++;                }            }        },0)    }}manipulate.init();var buf = document.getElementById("buf");buf.onclick = function(e){    manipulate.clickHander(e);}function cancel(){   if(id)   clearInterval(id)}function addCreatures(count){    for(var i=0;i<count;i++){        addCreature(i);    }}function init() {    var canvas =document.getElementById('main');    width = canvas.width = 400;    height = canvas.height = 400;    // alert(width+" "+height)    ctx = canvas.getContext('2d');    for(var i=0; i < 1; ++i) {        addCreature();    }    lastTime = (new Date()).getTime();    frames = 0;    totalTime = 0;    updateTime = 0;    updateFrames =0;    id = setInterval(update, 10);}function delay(time){    var st = new Date;    while(new Date - st < time);}function addCreature() {    var c = new Creature(Math.random()*100,Math.random()*200);    //delay(3000);    creats.push(c);}function update() {    var now = (new Date()).getTime();    delta = now-lastTime;    lastTime = now;    totalTime+=delta;    frames++;    updateTime+=delta;    updateFrames++;    if(updateTime > 1000) {        document.getElementById('fps').innerHTML = "FPS AVG: " + (1000*frames/totalTime).toFixed(2) + " CUR: " + (1000*updateFrames/updateTime).toFixed(2)+" number:"+creats.length;        updateTime = 0;        updateFrames =0;    }    for(var i=0; i < creats.length; ++i) {        creats[i].move();    }    draw();   // if(totalTime>5000) cancel();}function draw() {    ctx.clearRect(0,0,width,height);    creats.forEach(drawCreat);}function drawCreat(c,i,a) {    if (!onScreen(c)) {        return;    }    ctx.strokeStyle = "#FFFFFF";    ctx.fillStyle="red";    ctx.beginPath();    ctx.arc(c.x, c.y, 5, 0, Math.PI*2, true);     ctx.closePath();    ctx.stroke();    ctx.fill();}function onScreen(o) {    return o.x >= 0 && o.y >= 0 && o.x <= width && o.y <=height;}function Creature(x1,y) {    this.x = x1;    this.y = y;    this.dx = Math.random()*2;    this.dy = Math.random()*2;    this.move = function() {        this.x+=this.dx;        this.y+=this.dy;        if(this.x < 0 || this.x > width) {            this.dx*=-1;        }        if(this.y < 0 || this.y > height) {            this.dy*=-1;        }    }}init();</script></html>

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