A*寻路算法 (cocos2d-js详细代码)
看了几天的A*算法，感觉要成为一个游戏开发者，有必要把这个著名的算法拿到手。
网上有此算法的代码片段，但主要还是些模板类的伪代码，所以想分享一段完整的A*算法代码供大家更好的理解！（这里使用的是js语言和cocos2d游戏引擎）
对于A*算法概念性的描述，请看这里，本篇主要以代码为主。
下面是我的学习成果，有晦涩和需改进的地方欢迎吐槽！
var A_STAR_DISTANCE = 7; //像素大小，越小越精确，同时越耗时 var A_STAR_G_EXPEND_MIN = 10; //上下左右G值消耗数 var A_STAR_G_EXPEND_MAX = 14; //斜角G值消耗数 var HelloWorldLayer = cc.Layer.extend({ sprite:null, //角色 aStarPathArray:[], //最终角色要行走的路径 aStarBarrierArray:[], //地图障碍物 testNumber:1, ctor:function () { ////////////////////////////// // 1. super init first this._super(); ///////////////////////////// // 2. add a menu item with "X" image, which is clicked to quit the program // you may modify it. // ask director the window size var size = cc.director.getWinSize(); this.sprite = cc.Sprite.create(res.Plane_png); //角色初始化 this.sprite.attr({ x: 150, y: 50, rotation: 90 }); this.addChild(this.sprite, 0); var barrier1 = cc.rect(200,50,50,350); //绘制障碍物 var barrier2 = cc.rect(250,50,350,50); var barrier3 = cc.rect(250,350,350,50); this.aStarBarrierArray.push(barrier1); this.aStarBarrierArray.push(barrier2); this.aStarBarrierArray.push(barrier3); var drawBarrier = cc.DrawNode.create(); //在屏幕上显示障碍物 this.addChild(drawBarrier, 10); var vertices = [cc.p(200,50),cc.p(600,50),cc.p(600,100),cc.p(250,100),cc.p(250,350),cc.p(600,350),cc.p(600,400),cc.p(200,400)]; drawBarrier.drawPoly(vertices,null,2,cc.color(255,0,0,255)); if ('mouse' in cc.sys.capabilities) cc.eventManager.addListener({ event: cc.EventListener.MOUSE, onMouseUp:function(event){ if(event.getButton() != undefined) { var t = new Date().getTime(); event.getCurrentTarget().getStartAndEndPoint(event); //A*算法开始 cc.log("算法耗时:"+(new Date().getTime() - t)+"ms"); //计算起点到终点的算法耗时 } } }, this); return true; }, getStartAndEndPoint:function (event) { //得到起始点和终点坐标 var sp = {coordX:parseInt(this.sprite.x,10),coordY:parseInt(this.sprite.y,10)}; var ep = {coordX:parseInt(event.getLocation().x,10),coordY:parseInt(event.getLocation().y,10)}; var endPointIsObstacle = false; //判断终点是否在障碍物上，是的话就提示路径走不了 for (var theBarrierIndex=0; theBarrierIndex<this.aStarBarrierArray.length; theBarrierIndex++){ if(cc.rectContainsPoint(this.aStarBarrierArray[theBarrierIndex],cc.p(ep.coordX,ep.coordY))) { endPointIsObstacle = true; cc.log("你要去的位置有障碍物，请换条路线"); break; } } if(!endPointIsObstacle) this.findingPath(sp,ep); }, findingPath:function(startPoint,endPoint){ //A*算法 var openList = []; //初始化开启列表 var closeList = []; //初始化关闭列表 startPoint.ag = 0; startPoint.ah = 0; startPoint.af = startPoint.ag + startPoint.ah; //起点的G,H,F值为0 openList.push(startPoint); //起点加入开启列表 var findTheWay = false; do{ var centerNode = this.findMinNode(openList); //寻找F值最低的节点 openList.remove(centerNode); //将此节点从开启列表中删除，为了下次遍历开启列表的时候不再出现此节点 closeList.push(centerNode); //并将此节点加入到关闭列表 for(var i=0;i<8;i++) //遍历此节点周围的节点，并给这些节点加入坐标属性和G值 { var aroundNode = {}; switch (i){ case 0: aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE; //坐标属性 aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE; break; case 1: aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE; aroundNode.coordY = centerNode.coordY; break; case 2: aroundNode.coordX = centerNode.coordX+A_STAR_DISTANCE; aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE; break; case 3: aroundNode.coordX = centerNode.coordX; aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE; break; case 4: aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE; aroundNode.coordY = centerNode.coordY-A_STAR_DISTANCE; break; case 5: aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE; aroundNode.coordY = centerNode.coordY; break; case 6: aroundNode.coordX = centerNode.coordX-A_STAR_DISTANCE; aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE; break; case 7: aroundNode.coordX = centerNode.coordX; aroundNode.coordY = centerNode.coordY+A_STAR_DISTANCE; break; } for (var barrierIndex=0; barrierIndex<this.aStarBarrierArray.length; barrierIndex++){ aroundNode.isOb = cc.rectContainsPoint(this.aStarBarrierArray[barrierIndex],cc.p(aroundNode.coordX,aroundNode.coordY)); //判断当前节点是否在障碍物形成的方框里 if(aroundNode.isOb) break; } if (aroundNode.isOb){ //如果是障碍物，跳过 } else if(closeList.hasObject(aroundNode)){ //如果在关闭列表里，跳过 } else if(!openList.hasObject(aroundNode)){ //如果不在开启列表里，加入到开启列表 aroundNode.parentPath = centerNode; if (Math.abs(aroundNode.coordX-endPoint.coordX)<=A_STAR_DISTANCE/2 && Math.abs(aroundNode.coordY-endPoint.coordY)<=A_STAR_DISTANCE/2) //如果节点和终点的值相近，那么A*算法结束，得到路径 { findTheWay = true; var pathArry = []; this.gettingAStarPath(aroundNode,pathArry); //寻找路径 pathArry.splice(0,0,{starX:endPoint.coordX,starY:endPoint.coordY}); //加终点到数组头部 pathArry.splice(pathArry.length-1,1); //删一项数组底部的起点数据，此时的数组是最终的路径数组 this.aStarPathArray = []; this.aStarPathArray = pathArry; this.aStarPathArray.theIndex = this.aStarPathArray.length; this.unschedule(this.thePathSelector); this.schedule(this.thePathSelector,null,pathArry.length-1); break; //找到最短路径并跳出循环 } if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY) //确定中心节点和周围节点形成的角度，正交G值消耗10*像素，斜角G值消耗14*像素 aroundNode.ag = centerNode.ag + A_STAR_G_EXPEND_MAX*A_STAR_DISTANCE; else aroundNode.ag = centerNode.ag + A_STAR_G_EXPEND_MIN*A_STAR_DISTANCE; aroundNode.af = this.getAF(aroundNode,endPoint); openList.push(aroundNode); } else if(openList.hasObject(aroundNode)){ //如果在开启列表里 var newExpend = A_STAR_G_EXPEND_MIN*A_STAR_DISTANCE; if (aroundNode.coordX!=centerNode.coordX && aroundNode.coordY!=centerNode.coordY) //确定中心节点和周围节点形成的角度，正交G值消耗10*像素，斜角G值消耗14*像素 newExpend = A_STAR_G_EXPEND_MAX*A_STAR_DISTANCE; if (centerNode.ag + newExpend < aroundNode.ag){ //如果新的g值小于周围节点本身的g值，那么周围节点的父节点改为当前中心节点，并重新计算其F值 aroundNode.parentPath = centerNode; aroundNode.ag = centerNode.ag + newExpend; aroundNode.af = this.getAF(aroundNode,endPoint); } } } }while(!findTheWay) }, findMinNode:function(openListArray){ var minNode = openListArray[0]; for (var i=0;i<openListArray.length;i++) { if (minNode.af>openListArray[i].af) minNode=openListArray[i]; } return minNode; }, getAF:function(thisNode,endNode){ var aHExpend = (Math.abs(thisNode.coordX-endNode.coordX) + Math.abs(thisNode.coordY-endNode.coordY))*A_STAR_G_EXPEND_MIN; return aHExpend+thisNode.ag; }, gettingAStarPath:function(laseNode,array){ if(laseNode.parentPath != null) { array.push({starX:laseNode.parentPath.coordX,starY:laseNode.parentPath.coordY}); this.gettingAStarPath(laseNode.parentPath,array); } }, thePathSelector:function(){ this.roleRunThePath(this.aStarPathArray); }, roleRunThePath:function(array){ this.sprite.x = array[--array.theIndex].starX; this.sprite.y = array[array.theIndex].starY; } }); var HelloWorldScene = cc.Scene.extend({ onEnter:function () { this._super(); var layer = new HelloWorldLayer(); this.addChild(layer); } }); //这里给Array数组添加3个实例方法 Array.prototype.aStarIndexOf = function(val) { //通过对象寻找index值 for (var i = 0; i < this.length; i++) { if (this[i].coordX==val.coordX && this[i].coordY==val.coordY) return i; } return -1; }; Array.prototype.remove = function(val) { //删除相应的对象 var index = this.aStarIndexOf(val); if (index > -1) { this.splice(index, 1); } }; Array.prototype.hasObject = function(val){ //判断是否是同一个对象 for (var i = 0; i < this.length; i++){ if (this[i].coordX==val.coordX && this[i].coordY==val.coordY) return true; } return false; };
如下图，飞机在寻找路径的时候会避开红色区域。
