45-坦克斜穿过墙壁
8.15.7 坦克斜穿过墙壁
例8-19展示了一个地图设计不当的例子。如图8-19所示,坦克竟然可以斜着穿过墙壁。下面是例8-19的详细代码。
例8-19 地图设计不当的迷宫导致坦克斜着穿过墙壁
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Chapter 8 Example 19 - A* With Tank Animation with diagoinal moves</title>
<script src="modernizr.js"></script>
<script type='text/javascript' src='graph.js'></script>
<script type='text/javascript' src='astar.js'></script>
<script type="text/javascript">
window.addEventListener('load', eventWindowLoaded, false);
function eventWindowLoaded() {
canvasApp();
}
function canvasSupport () {
return Modernizr.canvas;
}
function canvasApp(){
if (!canvasSupport()) {
return;
}else{
var theCanvas = document.getElementById('canvas');
var context = theCanvas.getContext('2d');
}
var currentNodeIndex=0;
var nextNode;
var currentNode;
var rowDelta=0;
var colDelta=0;
var tankX=0;
var tankY=0;
var angleInRadians=0;
var tankStarted=false;
var tankMoving=false;
var finishedPath=false;
//设置区块地图
var mapRows=15;
var mapCols=15;
var tileMap=[
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
,[0,1,2,1,1,1,1,1,1,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,2,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,0,0,1,0,0,0,1,0,0,0,1,0]
,[0,1,1,1,2,1,0,0,0,1,1,1,1,1,0]
,[0,0,0,0,0,1,1,1,1,1,0,0,0,0,0]
,[0,1,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,2,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,1,1,1,1,1,2,1,1,1,1,1,1,0]
,[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
];
//设置 a* graph
var graph = new Graph(tileMap);
var startNode={x:4,y:1}; // use values of map turned on side
var endNode={x:13,y:10};
//创建节点列表
var start = graph.nodes[startNode.x][startNode.y];
var end = graph.nodes[endNode.x][endNode.y];
var result = astar.search(graph.nodes, start, end, true);
console.log("result", result);
//加载图片表
var tileSheet=new Image();
tileSheet.addEventListener('load', eventSheetLoaded , false);
tileSheet.src="tiles.png";
const FRAME_RATE=40;
var intervalTime=1000/FRAME_RATE;
function eventSheetLoaded() {
gameLoop();
}
function gameLoop() {
drawScreen();
window.setTimeout(gameLoop, intervalTime);
}
function drawScreen() {
for (var rowCtr=0;rowCtr<mapRows;rowCtr++) {
for (var colCtr=0;colCtr<mapCols;colCtr++){
var tileId=tileMap[rowCtr][colCtr];
var sourceX=Math.floor(tileId % 5) *32;
var sourceY=Math.floor(tileId / 5) *32;
context.drawImage(tileSheet,sourceX,
sourceY,32,32,colCtr*32,rowCtr*32,32,32);
}
}
//在起始点绘制绿色圆圈
context.beginPath();
context.strokeStyle="green";
context.lineWidth=5;
context.arc((startNode.y*32)+16, (startNode.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
//在终点绘制红色圆圈
context.beginPath();
context.strokeStyle="red";
context.lineWidth=5;
context.arc((endNode.y*32)+16, (endNode.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
//在路径上绘制黑色圆圈
for (var ctr=0;ctr<result.length-1;ctr++) {
var node=result[ctr];
context.beginPath();
context.strokeStyle="black";
context.lineWidth=5;
context.arc((node.y*32)+16, (node.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
}
if (!finishedPath) {
if (!tankStarted) {
currentNode=startNode;
tankStarted=true;
nextNode=result[0];
tankX=currentNode.x*32;
tankY=currentNode.y*32
}
if (tankX==nextNode.x*32 && tankY==nextNode.y*32) {
//节点变化
currentNodeIndex++;
if (currentNodeIndex == result.length) {
finishedPath=true;
}
currentNode=nextNode;
nextNode=result[currentNodeIndex]
tankMoving=false;
}
if (!finishedPath) {
if (nextNode.x > currentNode.x) {
colDelta=1;
}else if (nextNode.x < currentNode.x) {
colDelta=-1
}else{
colDelta=0
}
if (nextNode.y > currentNode.y) {
rowDelta=1;
}else if (nextNode.y < currentNode.y) {
rowDelta=-1
}else{
rowDelta=0
}
angleInRadians=Math.atan2(colDelta,rowDelta);
tankMoving=true;
}
tankX+=colDelta;
tankY+=rowDelta;
}
var tankSourceX=Math.floor(3 % 5) *32;
var tankSourceY=Math.floor(3 / 5) *32;
context.save(); //保存当前画布状态
context.setTransform(1,0,0,1,0,0); // 重置变换矩阵
context.translate((tankY)+16,(tankX)+16);
context.rotate(angleInRadians);
context.drawImage(tileSheet, tankSourceX, tankSourceY,32,32,-16,-16,32,32);
context.restore();
}
}
</script>
</head>
<body>
<div style="position: absolute; top: 50px; left: 50px;">
<canvas id="canvas" width="500" height="500">
Your browser does not support the HTML 5 Canvas.
</canvas>
</div>
</body>
</html>
图8-19是例8-19的运行截图。这个设计不当的地图导致坦克可以斜着穿过墙壁。后面的例子将会设计一张新的地图来修复这个问题。
例8-20将修改迷宫,在原来的坦克斜穿过墙壁的路口处添加一堵墙。下面是例8-20中的新地图。
var mapCols=15;
var tileMap=[
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
,[0,1,2,1,1,1,1,1,1,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,2,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,0,0,1,0,0,0,1,0,0,0,1,0]
,[0,1,1,1,2,1,0,0,0,1,1,1,1,1,0]
,[0,0,0,0,0,1,1,1,1,1,0,0,0,0,0]
,[0,1,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,2,0,0,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,1,1,1,1,1,2,1,1,1,1,1,1,0]
,[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
];
图8-20展示了在启用对角线选项下,新的地图对最短路径的影响。新增的墙壁改变了原来的路径,产生了一条新的不斜穿墙壁的路径。
例8-20 使用新的迷宫地图,排除墙壁被穿越的可能
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Chapter 8 Example 20 - A* With Tank Animation with new maze to prevent
passable walls </title>
<script src="modernizr.js"></script>
<script type='text/javascript' src='graph.js'></script>
<script type='text/javascript' src='astar.js'></script>
<script type="text/javascript">
window.addEventListener('load', eventWindowLoaded, false);
function eventWindowLoaded() {
canvasApp();
}
function canvasSupport () {
return Modernizr.canvas;
}
function canvasApp(){
if (!canvasSupport()) {
return;
}else{
var theCanvas = document.getElementById('canvas');
var context = theCanvas.getContext('2d');
}
var currentNodeIndex=0;
var nextNode;
var currentNode;
var rowDelta=0;
var colDelta=0;
var tankX=0;
var tankY=0;
var angleInRadians=0;
var tankStarted=false;
var tankMoving=false;
var finishedPath=false;
//set up tile map
var mapRows=15;
var mapCols=15;
var tileMap=[
[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
,[0,1,2,1,1,1,1,1,1,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,2,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,0,0,1,0,0,0,1,0,0,0,1,0]
,[0,1,1,1,2,1,0,0,0,1,1,1,1,1,0]
,[0,0,0,0,0,1,1,1,1,1,0,0,0,0,0]
,[0,1,1,1,1,1,0,0,0,1,1,1,1,1,0]
,[0,1,0,1,0,0,1,1,1,0,0,1,0,1,0]
,[0,1,0,1,0,0,2,0,0,0,0,1,0,1,0]
,[0,1,0,1,0,0,1,0,1,0,0,1,0,1,0]
,[0,1,1,1,1,1,1,2,1,1,1,1,1,1,0]
,[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
];
//设置 a* graph
var graph = new Graph(tileMap);
var startNode={x:4,y:1}; // use values of map turned on side
var endNode={x:13,y:10};
//创建节点列表
var start = graph.nodes[startNode.x][startNode.y];
var end = graph.nodes[endNode.x][endNode.y];
var result = astar.search(graph.nodes, start, end, true);
console.log("result", result);
//加载图片表
var tileSheet=new Image();
tileSheet.addEventListener('load', eventSheetLoaded , false);
tileSheet.src="tiles.png";
const FRAME_RATE=40;
var intervalTime=1000/FRAME_RATE;
function eventSheetLoaded() {
gameLoop();
}
function gameLoop() {
drawScreen();
window.setTimeout(gameLoop, intervalTime);
}
function drawScreen() {
for (var rowCtr=0;rowCtr<mapRows;rowCtr++) {
for (var colCtr=0;colCtr<mapCols;colCtr++){
var tileId=tileMap[rowCtr][colCtr];
var sourceX=Math.floor(tileId % 5) *32;
var sourceY=Math.floor(tileId / 5) *32;
context.drawImage(tileSheet,sourceX,
sourceY,32,32,colCtr*32,rowCtr*32,32,32);
}
}
//在起始点绘制绿色圆圈
context.beginPath();
context.strokeStyle="green";
context.lineWidth=5;
context.arc((startNode.y*32)+16, (startNode.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
//在终点绘制红色圆圈
context.beginPath();
context.strokeStyle="red";
context.lineWidth=5;
context.arc((endNode.y*32)+16, (endNode.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
//在路径上绘制黑色圆圈
for (var ctr=0;ctr<result.length-1;ctr++) {
var node=result[ctr];
context.beginPath();
context.strokeStyle="black";
context.lineWidth=5;
context.arc((node.y*32)+16, (node.x*32)+16, 10, 0,(Math.PI/180)*360,false);
context.stroke();
context.closePath();
}
if (!finishedPath) {
if (!tankStarted) {
currentNode=startNode;
tankStarted=true;
nextNode=result[0];
tankX=currentNode.x*32;
tankY=currentNode.y*32
}
if (tankX==nextNode.x*32 && tankY==nextNode.y*32) {
//节点变化
currentNodeIndex++;
if (currentNodeIndex == result.length) {
finishedPath=true;
}
currentNode=nextNode;
nextNode=result[currentNodeIndex]
tankMoving=false;
}
if (!finishedPath) {
if (nextNode.x > currentNode.x) {
colDelta=1;
}else if (nextNode.x < currentNode.x) {
colDelta=-1
}else{
colDelta=0
}
if (nextNode.y > currentNode.y) {
rowDelta=1;
}else if (nextNode.y < currentNode.y) {
rowDelta=-1
}else{
rowDelta=0
}
angleInRadians=Math.atan2(colDelta,rowDelta);
tankMoving=true;
}
tankX+=colDelta;
tankY+=rowDelta;
}
var tankSourceX=Math.floor(3 % 5) *32;
var tankSourceY=Math.floor(3 / 5) *32;
context.save(); //保存当前画布状态
context.setTransform(1,0,0,1,0,0); // 重置变换矩阵
context.translate((tankY)+16,(tankX)+16);
context.rotate(angleInRadians);
context.drawImage(tileSheet, tankSourceX, tankSourceY,32,32,-16,-16,32,32);
context.restore();
}
}
</script>
</head>
<body>
<div style="position: absolute; top: 50px; left: 50px;">
<canvas id="canvas" width="500" height="500">
Your browser does not support the HTML 5 Canvas.
</canvas>
</div>
</body>
</html>
针对A*寻路算法中的初级、中级以及更复杂的问题,本书全都介绍了一遍。读者可以在其他的应用中需要找到两点之间的最短路径时,简单地进行扩展和套用。