DEMO: http://cnwander.com/demo/billiards/
原文地址：http://cnwander.com/blog/?p=11
JS小游戏系列：
[JS小游戏]贪吃蛇+详细注释
先贴上代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>台球 by CNwander</title>
<style type="text/css">
* {margin:0; padding:0}
body {background:black; text-align:center; font-size:12px}
h1 {font-size:12px; color:gray; font-weight:normal; line-height:200%}
h1 .sub {vertical-align:super; color:red; font-size:9px; }
.info {position:absolute; right:0; color:gray}
#table {position:relative; width:800px; margin:20px auto 10px; height:544px; background:url(); _background:none; _filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(enabled='true', sizingMethod='scale', src="); _background:none; _filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(enabled='true', sizingMethod='scale', src="); _background:none; _filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(enabled='true', sizingMethod='scale', src=") no-repeat}
#force {position:absolute; left:0; top:18px; width:75px; height:20px; background:url() no-repeat; font-size:1px}
#scoreBoard {position:absolute; z-index:3; top:230px; left:346px; font-size:50px; color:white; filter:alpha(opacity=0); -moz-opacity:0; opacity:0}
#tips {padding:15px 0 0 20px; text-align:left; color:red; font-size:12px}
</style>
<script type="text/javascript">
// common
function $(str) {
return document.getElementById(str);
}
function $tag(str,target) {
target = target || document;
return target.getElementsByTagName(str);
}
function addEventHandler(obj,eType,fuc){
if(obj.addEventListener){
obj.addEventListener(eType,fuc,false);
}else if(obj.attachEvent){
obj.attachEvent("on" + eType,fuc);
}else{
obj["on" + eType] = fuc;
}
}
function removeEventHandler(obj,eType,fuc){
if(obj.removeEventListener){
obj.removeEventListener(eType,fuc,false);
}else if(obj.attachEvent){
obj.detachEvent("on" + eType,fuc);
}
}
function randowNum(start,end) {
return Math.floor(Math.random()*(end - start)) + start;
}
Array.prototype.remove=function(dx) {
if(isNaN(dx)||dx>this.length){return false;}
for(var i=0,n=0;i<this.length;i++)
{
if(this[i]!=this[dx])
{
this[n++]=this[i]
}
}
this.length-=1
}
//const
var TOTALR = 15, //球的半径(包括阴影)
R = 12, //球真实半径
POKER = 20,
W = 736, //案宽
H = 480, //案高
THICKNESS = 32, //边缘厚度
RATE = 100, //刷新频率
F = 0.01, //摩擦力
LOSS = 0.2, // 碰撞速度损失
TIPS = ["Tip1: 参考球，目标球，目标袋，三点一线，这是最基本的进球方法","Tip2: 右下角蓝条代表击球力度，小的力度更便于控制母球位置","Tip3: 右下角白球上的蓝点控制击球点，高杆，低杆，加塞都由它控制，高手与的区别往往在此","Tip4: 桌球，其实打的不是目标球，是母球"];
var table, //案子
cueBall, //母球
guideBall, //参考球
dotWrap, //参考线
speed = 12,
rollUp = 0,
rollRight = 0,
timer,
forceTimer,
balls = [],
movingBalls = [],
pokes = [[0,0],[W/2,-5],[W,0],[0,H],[W/2,H+5],[W,H]],
hasShot = false;
shots = 0; //连击次数
window.onload = function() {
initTable();
initShootPos();
showTips();
startGame();
}
function startGame() {
initBall();
addEventHandler(table,"mousemove",dragCueBall);
addEventHandler(table,"mouseup",setCueBall);
}
function initTable() {
table = $("table");
var dotWrapDiv = document.createElement("div"),
guideBallDiv = document.createElement("div");
dotWrapDiv.id = "dotWrap";
guideBallDiv.className = "guide ball";
setStyle(guideBallDiv,"display","none");
dotWrap = table.appendChild(dotWrapDiv);
guideBall = table.appendChild(guideBallDiv);
}
function initBall() {
//添加母球
cueBall = new Ball("cue",170,H/2);
balls.push(cueBall);
//添加目标球
for(var i = 0; i < 5; i++) {
for(var j = 0; j <= i; j++) {
var ball = new Ball("target",520 + i*2*R, H/2 - R*i + j*2*R);
balls.push(ball);
}
}
}
function initShootPos() {
var wrap = $("shootPos"),
handler = $("dot"),
arrowR = 18;
addEventHandler(wrap,"mousedown",selectDot);
function selectDot(e) {
e = e || event;
var pos = getElemPos(wrap),
x = e.clientX - pos[0] - handler.offsetWidth/2,
y = e.clientY - pos[1] - handler.offsetHeight/2;
if(Math.sqrt((x-22)*(x-22) + (y-22)*(y-22)) > arrowR) {
var angle = Math.atan2(x-22,y-22);
x = arrowR*Math.sin(angle) + 22;
y = arrowR*Math.cos(angle) + 22;
}
setPos(handler,x,y);
}
}
function getElemPos(target,reference) {
reference = reference || document;
var left = 0,top = 0;
return getPos(target);
function getPos(target) {
if(target != reference) {
left += target.offsetLeft;
top += target.offsetTop;
return getPos(target.parentNode);
} else {
return [left,top];
}
}
}
// ball class
function Ball(type,x,y) {
var div = document.createElement("div");
div.className = type + " ball";
this.elem = table.appendChild(div);
this.type = type;
this.x = x; //位置
this.y = y;
this.angle = 0; //角度
this.v = 0; //速度(不包含方向)
setBallPos(this.elem,x,y);
return this;
}
function setCueBall() {
removeEventHandler(table,"mousemove",dragCueBall);
removeEventHandler(table,"mouseup",setCueBall);
startShot();
}
function startShot() {
show(cueBall.elem);
addEventHandler(table,"mousemove",showGuide);
addEventHandler(table,"mousedown",updateForce);
addEventHandler(table,"mouseup",shotCueBall);
}
function dragCueBall(e) {
var toX,toY;
e = e || event;
toX = e.clientX - table.offsetLeft - THICKNESS,
toY = e.clientY - table.offsetTop - THICKNESS;
toX = toX >= R ? toX : R;
toX = toX <= 170 ? toX : 170;
toY = toY >= R ? toY : R;
toY = toY <= H - R ? toY : H - R;
setBallPos(cueBall,toX,toY);
}
function shotCueBall() {
removeEventHandler(table,"mousemove",showGuide);
removeEventHandler(table,"mousedown",updateForce);
removeEventHandler(table,"mouseup",shotCueBall);
window.clearInterval(forceTimer);
speed = $("force").offsetWidth * 0.15;
var dotDisX = $("dot").offsetLeft-22,
dotDisY = $("dot").offsetTop-22,
dotDis = Math.sqrt(dotDisX*dotDisX + dotDisY*dotDisY),
dotAngle = Math.atan2(dotDisX,dotDisY);
rollRight = Math.round(dotDis*Math.sin(dotAngle))/5;
rollUp = -Math.round(dotDis*Math.cos(dotAngle))/5;
var formPos = getBallPos(cueBall.elem),
toPos = getBallPos(guideBall),
angle = Math.atan2(toPos[0] - formPos[0],toPos[1] - formPos[1]);
hide(dotWrap);
hide(guideBall);
cueBall.v = speed;
cueBall.angle = angle;
movingBalls.push(cueBall);
timer = window.setInterval(roll,1000 / RATE);
}
function showGuide(e) {
var fromX,fromY,toX,toY;
e = e || event;
toX = e.clientX - table.offsetLeft - THICKNESS,
toY = e.clientY - table.offsetTop - THICKNESS;
setBallPos(guideBall,toX,toY);
show(dotWrap);
show(guideBall);
drawLine();
//参考线
function drawLine() {
var dotNum = 16,
pos = getBallPos(cueBall.elem);
dotWrap.innerHTML = "";
fromX = pos[0];
fromY = pos[1];
var partX = (toX - fromX) / dotNum,
partY = (toY - fromY) / dotNum;
for(var i = 1; i < dotNum; i++) {
var x = fromX + partX * i,
y = fromY + partY * i;
drawDot(dotWrap, x, y);
}
}
}
function roll() {
if(movingBalls.length <= 0) {
if(!hasShot) shots = 0;
else shots ++; //累计连击
hasShot = false;
setStyle($("force"),"width",80+"px");
setPos($("dot"),22,22);
window.clearInterval(timer);
if(shots > 1) showScore(shots); //显示连击数
startShot();
}
for(var i = 0; i < movingBalls.length; i++) {
var ball = movingBalls[i],
sin = Math.sin(ball.angle),
cos = Math.cos(ball.angle);
ball.v -= F;
//移除静止的小球
if(Math.round(ball.v) == 0) {
ball.v = 0;
movingBalls.remove(i);
continue;
}
var vx = ball.v * sin,
vy = ball.v * cos;
ball.x += vx;
ball.y += vy;
//入袋
if(isPocket(ball.x,ball.y)) {
hide(ball.elem);
if(ball.type == "cue") {
if(!hasShot) shots = 0;
hasShot = false;
window.setTimeout(function(){
ball.v = 0;
setBallPos(ball,170,250);
},500);
}else {
//移除入袋小球
hasShot = true;
ball.v = 0;
for(var k = 0, l =0; k < balls.length; k++) {
if(balls[k] != ball) {
balls[l++] = balls[k];
}
}
balls.length -= 1;
}
return;
}
//边缘碰撞
if(ball.x < R || ball.x > W - R) {
ball.angle *= -1;
ball.angle %= Math.PI;
ball.v = ball.v * (1 - LOSS);
vx = ball.v*Math.sin(ball.angle);
vy = ball.v*Math.cos(ball.angle);
if(ball.x < R) ball.x = R;
if(ball.x > W - R) ball.x = W - R;
//母球加塞
if(ball.type == "cue") {
if(ball.angle > 0) vy -= rollRight;
else vy += rollRight;
vx += rollUp;
rollUp *= 0.2;
rollRight *= 0.2;
ball.v = Math.sqrt(vx*vx + vy*vy);
ball.angle = Math.atan2(vx,vy);
}
}
if(ball.y < R || ball.y > H - R) {
ball.angle = ball.angle > 0 ? Math.PI - ball.angle : - Math.PI - ball.angle ;
ball.angle %= Math.PI;
ball.v = ball.v * (1 - LOSS);
vx = ball.v*Math.sin(ball.angle);
vy = ball.v*Math.cos(ball.angle);
if(ball.y < R) ball.y = R;
if(ball.y > H - R) ball.y = H - R;
//母球加塞
if(ball.type == "cue") {
if(Math.abs(ball.angle) < Math.PI/2) vx += rollRight;
else vx -= rollRight;
vy += rollUp;
rollUp *= 0.2;
rollRight *= 0.2;
ball.v = Math.sqrt(vx*vx + vy*vy);
ball.angle = Math.atan2(vx,vy);
}
}
//小球碰撞
for(var j = 0; j < balls.length; j++) {
var obj = balls[j];
if(obj == ball) continue;
var disX = obj.x - ball.x,
disY = obj.y - ball.y,
gap = 2 * R;
if(disX <= gap && disY <= gap) {
var dis = Math.sqrt(Math.pow(disX,2)+Math.pow(disY,2));
if(dis <= gap) {
//如果是静止的，则添加到数组movingBalls
if(Math.round(obj.v) == 0)
movingBalls.push(obj);
//将坐标旋转到x轴进行碰撞计算
// 计算角度和正余弦值 - 精确值
//var c = (obj.x*ball.y - obj.y*ball.x)/(2*R),
// d = Math.sqrt(ball.x*ball.x + ball.y*ball.y),
// angle = Math.asin(ball.y/d) - Math.asin(c/d) - ball.angle%(Math.PI/2),
//angle = Math.asin(oy / (2 * R)),
//还原两球相切状态 - 近似值
ball.x -= (gap - dis)*sin;
ball.y -= (gap - dis)*cos;
disX = obj.x - ball.x;
disY = obj.y - ball.y;
// 计算角度和正余弦值
var angle = Math.atan2(disY, disX),
hitsin = Math.sin(angle),
hitcos = Math.cos(angle),
objVx = obj.v * Math.sin(obj.angle),
objVy = obj.v * Math.cos(obj.angle);
//trace(angle*180/Math.PI);
// 旋转坐标
var x1 = 0,
y1 = 0,
x2 = disX * hitcos + disY * hitsin,
y2 = disY * hitcos - disX * hitsin,
vx1 = vx * hitcos + vy * hitsin,
vy1 = vy * hitcos - vx * hitsin,
vx2 = objVx * hitcos + objVy * hitsin,
vy2 = objVy * hitcos - objVx * hitsin;
// 碰撞后的速度和位置
var plusVx = vx1 - vx2;
vx1 = vx2;
vx2 = plusVx + vx1;
//母球加塞
if(ball.type == "cue") {
vx1 += rollUp;
rollUp *= 0.2;
}
x1 += vx1;
x2 += vx2;
// 将位置旋转回来
var x1Final = x1 * hitcos - y1 * hitsin,
y1Final = y1 * hitcos + x1 * hitsin,
x2Final = x2 * hitcos - y2 * hitsin,
y2Final = y2 * hitcos + x2 * hitsin;
obj.x = ball.x + x2Final;
obj.y = ball.y + y2Final;
ball.x = ball.x + x1Final;
ball.y = ball.y + y1Final;
// 将速度旋转回来
vx = vx1 * hitcos - vy1 * hitsin;
vy = vy1 * hitcos + vx1 * hitsin;
objVx = vx2 * hitcos - vy2 * hitsin;
objVy = vy2 * hitcos + vx2 * hitsin;
//最终速度
ball.v = Math.sqrt(vx*vx + vy*vy) * (1 - 0);
obj.v = Math.sqrt(objVx*objVx + objVy*objVy) * (1 - 0);
// 计算角度
ball.angle = Math.atan2(vx , vy);
obj.angle = Math.atan2(objVx , objVy);
//break;
}
}
}
setBallPos(ball,ball.x,ball.y);
}
}
function isPocket(x,y) {
if(y < POKER) return check(0,2);
else if (y > H - POKER) return check(3,5);
else return false;
function check(m,n) {
for(var i=m; i<=n; i++) {
if(x >= pokes[i][0] - POKER && x <= pokes[i][0] + POKER) {
var dis = Math.sqrt(Math.pow(x - pokes[i][0],2) + Math.pow(y - pokes[i][1],2));
if(dis <= POKER) return true;
else return false;
}
}
}
}
function getBallPos(obj) {
var pos = [];
pos.push(obj.offsetLeft - THICKNESS + TOTALR);
pos.push(obj.offsetTop - THICKNESS + TOTALR);
return pos;
}
function setPos(obj,x,y) {
obj.style.left = x + "px";
obj.style.top = y + "px";
}
function setBallPos(ball,x,y) {
if(ball.constructor == Ball) {
ball.x = x;
ball.y = y;
ball = ball.elem;
}
setPos(ball,x + THICKNESS - TOTALR,y + THICKNESS - TOTALR);
}
function drawDot(wrap,x,y) {
var elem = document.createElement("div");
setStyle(elem,{
position: "absolute",
width: "1px",
height: "1px",
fontSize: "1px",
background: "white"
});
setPos(elem,x,y);
wrap.appendChild(elem);
}
function updateForce() {
var obj = $("force"),
len = 80,
up = true;
forceTimer = window.setInterval(update,10);
function update() {
if(up) setStyle(obj,"width",len+++"px");
else setStyle(obj,"width",len--+"px");
if(len > 136) up = false;
if(len <= 0) up = true;
}
}
function setStyle() {
if(arguments.length == 2 && typeof arguments[1] == "object") {
for(var key in arguments[1]) {
arguments[0].style[key] = arguments[1][key];
}
} else if (arguments.length > 2) {
arguments[0].style[arguments[1]] = arguments[2];
}
}
function hide(obj) {
setStyle(obj,"display","none");
}
function show(obj) {
setStyle(obj,"display","block");
}
//输出信息
function trace(sth,who) {
who = who || $("tips");
if(document.all) who.innerText = sth;
else who.textContent = sth;
return who;
}
function showScore(n) {
var wrap = $("scoreBoard");
trace(n+"连杆",wrap);
fadeIn(wrap);
}
function fadeIn(obj){
var fromY = 230,
posStep = [8,14,19,23,26,28,29,29,30,30,30],
opaStep = [0,0.05,0.1,0.15,0.2,0.25,0.3,0.4,0.5,0.6,0.8],
fromOpa = 0,
t = 0,
step = posStep.length,
inTimer = window.setInterval(showIn,20),
outTimer;
function showIn() {
setOpacity(obj,opaStep[t]);
obj.style.top = fromY + posStep[t] + "px";
t++;
if(t>=step) {
window.clearInterval(inTimer);
outTimer = window.setInterval(fadeOut,50);
}
}
function fadeOut() {
t--;
setOpacity(obj,opaStep[t]);
obj.style.top = fromY + posStep[t] + "px";
if(t <= 0) {
window.clearInterval(outTimer);
hide(obj);
}
}
}
function setOpacity(obj,n) {
obj.style.cssText = "filter:alpha(opacity="+ n*100 +"); -moz-opacity:"+ n +"; opacity:"+ n;
}
function showTips() {
var i = 0;
tip();
window.setInterval(tip,3000);
function tip() {
trace(TIPS[i++]);
if(i >= TIPS.length) i = 0;
}
}
</script>
</head>
<body>
<div class="info">探讨： <a href="http://bbs.blueidea.com/thread-2951566-1-1.html">Blueidea</a> <a href="http://cnwander.com/blog/?p=11">Wander's space</a></div>
<h1>中国人民烎起来！<span class="sub">60周年</span></h1>
<div id="table">
<div id="scoreBoard"></div>
</div>
<div class="bot">
<div id="tips"></div>
<div class = "ctrl">
<div id="force"></div>
<div id="shootPos">
<div id="dot"></div>
</div>
</div>
</div>
</body>
</html>
虽厚颜冠名桌球，其实与真实桌球还相差甚远，还有太多需要改进的地方。
具体待解决的问题：
其它肯定还会有很多问题，担心假期把心玩油了，回头没心思继续，干脆一气呵成，赶得有些匆忙，问题回头再慢慢解决吧，先发上来，对这块有兴趣的同学一块儿探讨探讨。
大学数学基本是过场，高中的物理数学与忘得所剩无几，真正做东西才发现自己这块太薄弱，希望在这方面经验比较丰富的同学不吝赐教。
 no-repeat}<br />
.ball {position:absolute; width:30px; height:30px}<br />
#dotWrap {position:absolute; z-index:2; left:32px; top:32px; width:736px; height:480px}<br />
.guide {z-index:3; background-image:url(<a href=){kind=link}