用HTML5-Canvas 写一个桌球游戏DEMO

用HTML5-Canvas 写一个桌球游戏DEMO

更新: 2017-06-21

来源:9秒社团

阅读:733

这只是一个简单的DEMO。游戏性、游戏规则没怎么考虑,如果有兴趣细化的朋友可以细化一下,比如细化一下规则,游戏开关,加个声音,细化一下进球检测,更严谨甚至可以去查下击球力度、桌面真实摩擦力等来把游戏弄的更像游戏。我只是给个编程思路,做一个DEMO而已,玩起来估计还是会很爽快的。

【球】

var Ball = function(x , y , ismine){
            this.x = x;
            this.y = y;
            this.ismine = ismine;
            this.oldx = x;
            this.oldy = y;
            this.vx = 0;
            this.vy = 0;
            this.radius = ballRadius;
            this.inhole = false;this.moving = true;
        }
        Ball.prototype = {
            constructor:Ball,
            _paint:function(){
                var b = this.ismine?document.getElementById("wb") : document.getElementById("yb")
                if(b.complete) {
                    ctx.drawImage(b , this.x-this.radius , this.y-this.radius , 2*this.radius , 2*this.radius);
                }
                else {
                    b.onload = function(){
                        ctx.drawImage(b , this.x-this.radius , this.y-this.radius , 2*this.radius , 2*this.radius);
                    }
                }
            },
            _run:function(t){
                this.oldx = this.x;
                this.oldy = this.y;

                this.vx = Math.abs(this.vx)<0.1? 0 : (this.vx>0? this.vx-mcl*t : this.vx+mcl*t);
                 this.vy = Math.abs(this.vy)<0.1? 0 : (this.vy>0? this.vy-mcl*t : this.vy+mcl*t);
                // this.vx += this.vx>0? -mcl*t : mcl*t;
                // this.vy += this.vy>0? -mcl*t : mcl*t;

                 this.x += t * this.vx * pxpm;
                 this.y += t * this.vy * pxpm;

                 if((this.x<50 && this.y<50) || (this.x>370 && this.x<430 && this.y<50) || (this.x > 758 && this.y<50) || (this.x<46 && this.y>490) || (this.x>377 && this.x<420 && this.y>490) || (this.x > 758 && this.y>490)){
                     this.inhole = true;
                     if(this.ismine){
                         var that = this;
                         setTimeout(function(){
                             that.x = 202;
                             that.y = canvas.height/2;
                             that.vx = 0;
                             that.vy = 0;
                             that.inhole = false;
                         } , 500)
                     }
                     else {
                         document.getElementById("shotNum").innerHTML = parseInt(document.getElementById("shotNum").innerHTML)+1
                     }
                 }
                 else {
                     if(this.y > canvas.height - (ballRadius+tbw) || this.y < (ballRadius+tbw)){
                         this.y = this.y < (ballRadius+tbw) ? (ballRadius+tbw) : (canvas.height - (ballRadius+tbw));
                         this.derectionY = !this.derectionY;
                         this.vy = -this.vy*0.6;
                     }
                     if(this.x > canvas.width - (ballRadius+tbw) || this.x < (ballRadius+tbw)){
                         this.x = this.x < (ballRadius+tbw) ? (ballRadius+tbw) : (canvas.width - (ballRadius+tbw));
                         this.derectionX = !this.derectionX;
                         this.vx = -this.vx*0.6;
                     }
                 }
                 this._paint();

                 if(Math.abs(this.vx)<0.1 && Math.abs(this.vy)<0.1){
                     this.moving = false;
                 }
                 else {
                     this.moving = true;
                 }
            }
        }
球类的属性:x,y球的位置,vx,vy球的水平速度以及求得垂直速度,ismine代表是白球还是其他球(不同球在_paint方法中绘制的图片不一样),oldx,oldy用于保存球的上一帧位置,不过暂时还没用上,应该有用吧。_paint方法没什么好说的,_run方法就是跟踪小球位置,根据小球每一帧的时间来算出小球的位移增量以及速度增量,mcl和pxpm都是常量,mcl是摩擦力,pxpm是大概算个像素和现实转换比例。。。。然后就是碰撞检测,这个很容易理解了,就计算小球的位置有没有超过边界,超过了就反弹。不过这种碰撞检测很不严谨,如果真要做游戏建议用更复杂一些的。还有就是根据小球的速度来让小球静止。


【辅助线】


var dotLine = function(x0,y0,x1,y1){
            this.x0 = this.x0;
            this.y0 = this.y0;
            this.x1 = this.x1;
            this.y1 = this.y1;
            this.dotlength = 3;
            this.display = false;
        }
        dotLine.prototype = {
            constructor:dotLine,
            _ready:function(){
                this.length = Math.sqrt(Math.pow(this.y1 - this.y0 , 2)+Math.pow(this.x1 - this.x0 , 2));
                this.dotNum = Math.ceil(this.length/this.dotlength);
            },
            _paint:function(){
                this._ready();
                xadd = this.dotlength*(this.x1 - this.x0)/this.length;
                yadd = this.dotlength*(this.y1 - this.y0)/this.length;
                ctx.save();
                ctx.beginPath();
                for(var i=1;i<=this.dotNum;i++){
                    if(i%2!==0){
                        ctx.moveTo(this.x0+(i-1)*xadd , this.y0+(i-1)*yadd);
                        ctx.lineTo(this.x0+i*xadd , this.y0+i*yadd);
                    }
                }
                ctx.strokeStyle = "#FFF";
                ctx.stroke();
                ctx.beginPath();
                ctx.arc(this.x1 , this.y1 , ballRadius-2 , 0 , 2*Math.PI);
                ctx.stroke();
                ctx.restore();
            }
        }


画虚线,这个比较简单了,获取鼠标的位置和白球位置,然后在两者之间隔一段距离画条线,然后就成虚线了。

【多球碰撞检测】


function collision(){
            for(var i=0;i<balls.length;i++){
                for(var j=0;j<balls.length;j++){
                    var b1 = balls[i],b2 = balls[j];
                    if(b1 !== b2 && !b1.inhole && !b2.inhole){
                        var rc = Math.sqrt(Math.pow(b1.x - b2.x , 2) + Math.pow(b1.y - b2.y , 2));
                        if(Math.ceil(rc) < (b1.radius + b2.radius)){
                            if(!b1.moving && !b2.moving) return;
                            //获取碰撞后的速度增量
                            var ax = ((b1.vx - b2.vx)*Math.pow((b1.x - b2.x) , 2) + (b1.vy - b2.vy)*(b1.x - b2.x)*(b1.y - b2.y))/Math.pow(rc , 2)
                            var ay = ((b1.vy - b2.vy)*Math.pow((b1.y - b2.y) , 2) + (b1.vx - b2.vx)*(b1.x - b2.x)*(b1.y - b2.y))/Math.pow(rc , 2)
                //将速度增量赋给碰撞小球
                            b1.vx = b1.vx-ax;
                            b1.vy = b1.vy-ay;
                            b2.vx = b2.vx+ax;
                            b2.vy = b2.vy+ay;
                //修正小球碰撞距离
                            var clength = ((b1.radius+b2.radius)-rc)/2;
                            var cx = clength * (b1.x-b2.x)/rc;
                            var cy = clength * (b1.y-b2.y)/rc;
                            b1.x = b1.x+cx;
                            b1.y = b1.y+cy;
                            b2.x = b2.x-cx;
                            b2.y = b2.y-cy;
                        }
                    }
                }
            }
        }
对所有小球进行遍历,计算两个小球的球心距离,如果小于两小球的半径和,则说明发生了碰撞。如果两个小球都是静止的,就不进行碰撞检测,否则进行计算碰撞后的速度增量,碰撞速度增量的求法可以直接看 小球碰撞的算法设计 ,里面讲的挺详细的,综合起来就得出了上面那一串式子了。
将速度增量赋给碰撞小球。因为两个球碰撞那一帧,两个球是有部分重叠的,所以得进行位置修正,不然小球会一直处于碰撞然后就黏在一起了,位置修正的原理也简单,算出两球的球心距离,通过勾股定理计算出两球的重叠区域的宽度,然后把宽度除于2后赋给小球新的位置,新的位置就是两个球的半径刚好等于球心距。

【鼠标动作】



canvas.addEventListener("mousedown" , function(){
            if(balls[0].moving) return;

            document.querySelector(".shotPower").style.display = "block";
            document.querySelector(".shotPower").style.top = balls[0].y-60 + "px";
            document.querySelector(".shotPower").style.left = balls[0].x-40 +"px";
            document.getElementById("pow").className = "animate";
            var x = event.clientX + document.body.scrollLeft + document.documentElement.scrollLeft - document.querySelector(".view").offsetLeft;
            var y = event.clientY + document.body.scrollTop + document.documentElement.scrollTop - document.querySelector(".view").offsetTop;
            dotline.display = true;
            dotline.x0 = balls[0].x;
            dotline.y0 = balls[0].y;
            dotline.x1 = x;
            dotline.y1 = y;

            window.addEventListener("mouseup" , muHandle , false);
            window.addEventListener("mousemove" , mmHandle , false);

            function mmHandle(){
                var x = event.clientX + document.body.scrollLeft + document.documentElement.scrollLeft - document.querySelector(".view").offsetLeft;
                var y = event.clientY + document.body.scrollTop + document.documentElement.scrollTop - document.querySelector(".view").offsetTop;
                dotline.x1 = x;
                dotline.y1 = y;
            }
            function muHandle(){
                var x = event.clientX + document.body.scrollLeft + document.documentElement.scrollLeft - document.querySelector(".view").offsetLeft;
                var y = event.clientY + document.body.scrollTop + document.documentElement.scrollTop - document.querySelector(".view").offsetTop;

                var angle = Math.atan((y - balls[0].y)/(x - balls[0].x));
                var h = document.getElementById("pow").offsetHeight/document.getElementById("powbar").offsetHeight;
                var v = 60*h;
                document.getElementById("pow").style.height = h*100+"%"

                balls[0].vx = x - balls[0].x>0 ? v*Math.abs(Math.cos(angle)) : -v*Math.abs(Math.cos(angle)); 
                balls[0].vy = y - balls[0].y>0 ? v*Math.abs(Math.sin(angle)) : -v*Math.abs(Math.sin(angle));

                document.getElementById("pow").className = "";

                window.removeEventListener("mouseup" , muHandle , false);
                window.removeEventListener("mousemove" , muHandle , false);
                dotline.display = false;
                document.querySelector(".shotPower").style.display = "none";
            }
        },false);
鼠标动作也比较简单,有js基础的基本上都没问题,就是鼠标按下后计算鼠标位置,然后产生辅助虚线,鼠标移动后修改辅助虚线的终点位置。鼠标按下的时候旁边产生一个力量计,我就只用用animation做动画了,然后鼠标按键抬起时通过计算力量计的大小来确定白球的速度,然后再分解成水平速度以及垂直速度赋给白球。同时取消鼠标移动以及鼠标抬起的事件绑定,把辅助虚线以及力量计隐藏。


【动画舞台】


  function animate(){
            ctx.clearRect(0,0,canvas.width,canvas.height)
             var t1 = new Date();
             var t = (t1 - t0)/1000;

             collision();
             balls.foreach(function(){
                 if(!this.inhole) this._run(t);
             });
             if(dotline.display){
                 dotline.x0 = balls[0].x;
                 dotline.y0 = balls[0].y;
                 dotline._paint();
             }

             t0 = t1;
             if(!animateStop){
                 if("requestAnimationFrame" in window){
                     requestAnimationFrame(animate);
                 }
                 else if("webkitRequestAnimationFrame" in window){
                     webkitRequestAnimationFrame(animate);
                 }
                 else if("msRequestAnimationFrame" in window){
                     msRequestAnimationFrame(animate);
                 }
                 else if("mozRequestAnimationFrame" in window){
                     mozRequestAnimationFrame(animate);
                 }
                 else {
                     setTimeout(animate , 16);
                 }
             }
        }
这个就是游戏每一帧的逻辑处理现场,如果小球进洞了,就不再进行绘制,如果辅助虚线的display属性设成false,就不进行辅助虚线的绘制,还有就是计算每一帧的时间。

【常量与初始化】

var canvas = document.getElementById("cas");
        var ctx = canvas.getContext('2d');
        var mcl = 1 , collarg = 0.8 , ballRadius = 15 , t0 = 0 , balls=[] , tbw = 32 , animateStop = true , powAnimation = false;
        var dotline;
        pxpm = canvas.width/20;

        window.onload = function(){
            var myball = new Ball(202 , canvas.height/2 , true);
            balls.push(myball);
            for(var i=0;i<6;i++){
                for(var j=0;j<i;j++){
                    var other = new Ball(520+i*(ballRadius-2)*2 , (canvas.height-i*2*ballRadius)/2+ballRadius+2*ballRadius*j , false);
                    balls.push(other);
                }
            }
            t0 = new Date();
            dotline = new dotLine(0,0,0,0);
            animateStop = false;
            animate();
        }
底部的那两个方法是写两条线相交的判定和交点的获取,实例化所有小球,把小球全部按照规律摆好,然后获取当前时间,实例化辅助虚线,动画开始。