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html5-tower-defense-master/src/js/td-walk.js
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html5-tower-defense-master/src/js/td-walk.js
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/*
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* Copyright (c) 2011.
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*
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* Author: oldj <oldj.wu@gmail.com>
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* Blog: http://oldj.net/
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*
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* Last Update: 2011/1/10 5:22:52
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*/
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// _TD.a.push begin
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_TD.a.push(function (TD) {
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/**
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* 使用 A* 算法（Dijkstra算法？）寻找从 (x1, y1) 到 (x2, y2) 最短的路线
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*
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*/
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TD.FindWay = function (w, h, x1, y1, x2, y2, f_passable) {
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this.m = [];
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this.w = w;
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this.h = h;
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this.x1 = x1;
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this.y1 = y1;
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this.x2 = x2;
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this.y2 = y2;
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this.way = [];
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this.len = this.w * this.h;
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this.is_blocked = this.is_arrived = false;
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this.fPassable = typeof f_passable == "function" ? f_passable : function () {
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return true;
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};
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this._init();
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};
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TD.FindWay.prototype = {
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_init: function () {
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if (this.x1 == this.x2 && this.y1 == this.y2) {
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// 如果输入的坐标已经是终点了
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this.is_arrived = true;
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this.way = [
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[this.x1, this.y1]
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];
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return;
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}
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for (var i = 0; i < this.len; i++)
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this.m[i] = -2; // -2 表示未探索过，-1 表示不可到达
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this.x = this.x1;
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this.y = this.y1;
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this.distance = 0;
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this.current = [
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[this.x, this.y]
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]; // 当前一步探索的格子
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this.setVal(this.x, this.y, 0);
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while (this.next()) {
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}
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},
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getVal: function (x, y) {
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var p = y * this.w + x;
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return p < this.len ? this.m[p] : -1;
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},
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setVal: function (x, y, v) {
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var p = y * this.w + x;
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if (p > this.len) return false;
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this.m[p] = v;
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},
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/**
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* 得到指定坐标的邻居，即从指定坐标出发，1 步之内可以到达的格子
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* 目前返回的是指定格子的上、下、左、右四个邻格
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* @param x {Number}
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* @param y {Number}
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*/
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getNeighborsOf: function (x, y) {
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var nbs = [];
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if (y > 0) nbs.push([x, y - 1]);
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if (x < this.w - 1) nbs.push([x + 1, y]);
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if (y < this.h - 1) nbs.push([x, y + 1]);
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if (x > 0) nbs.push([x - 1, y]);
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return nbs;
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},
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/**
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* 取得当前一步可到达的 n 个格子的所有邻格
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*/
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getAllNeighbors: function () {
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var nbs = [], nb1, i, c, l = this.current.length;
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for (i = 0; i < l; i++) {
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c = this.current[i];
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nb1 = this.getNeighborsOf(c[0], c[1]);
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nbs = nbs.concat(nb1);
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}
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return nbs;
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},
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/**
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* 从终点倒推，寻找从起点到终点最近的路径
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* 此处的实现是，从终点开始，从当前格子的邻格中寻找值最低（且大于 0）的格子，
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* 直到到达起点。
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* 这个实现需要反复地寻找邻格，有时邻格中有多个格子的值都为最低，这时就从中
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* 随机选取一个。还有一种实现方式是在一开始的遍历中，给每一个到达过的格子添加
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* 一个值，指向它的来时的格子（父格子）。
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*/
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findWay: function () {
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var x = this.x2,
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y = this.y2,
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nb, max_len = this.len,
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nbs_len,
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nbs, i, l, v, min_v = -1,
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closest_nbs;
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while ((x != this.x1 || y != this.y1) && min_v != 0 &&
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this.way.length < max_len) {
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this.way.unshift([x, y]);
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nbs = this.getNeighborsOf(x, y);
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nbs_len = nbs.length;
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closest_nbs = [];
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// 在邻格中寻找最小的 v
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min_v = -1;
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for (i = 0; i < nbs_len; i++) {
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v = this.getVal(nbs[i][0], nbs[i][1]);
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if (v < 0) continue;
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if (min_v < 0 || min_v > v)
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min_v = v;
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}
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// 找出所有 v 最小的邻格
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for (i = 0; i < nbs_len; i++) {
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nb = nbs[i];
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if (min_v == this.getVal(nb[0], nb[1])) {
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closest_nbs.push(nb);
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}
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}
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// 从 v 最小的邻格中随机选取一个作为当前格子
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l = closest_nbs.length;
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i = l > 1 ? Math.floor(Math.random() * l) : 0;
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nb = closest_nbs[i];
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x = nb[0];
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y = nb[1];
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}
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},
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/**
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* 到达终点
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*/
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arrive: function () {
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this.current = [];
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this.is_arrived = true;
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this.findWay();
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},
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/**
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* 道路被阻塞
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*/
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blocked: function () {
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this.current = [];
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this.is_blocked = true;
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},
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/**
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* 下一次迭代
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* @return {Boolean} 如果返回值为 true ，表示未到达终点，并且道路
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* 未被阻塞，可以继续迭代；否则表示不必继续迭代
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*/
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next: function () {
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var neighbors = this.getAllNeighbors(), nb,
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l = neighbors.length,
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valid_neighbors = [],
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x, y,
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i, v;
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this.distance++;
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for (i = 0; i < l; i++) {
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nb = neighbors[i];
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x = nb[0];
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y = nb[1];
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if (this.getVal(x, y) != -2) continue; // 当前格子已探索过
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//grid = this.map.getGrid(x, y);
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//if (!grid) continue;
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if (this.fPassable(x, y)) {
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// 可通过
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/**
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* 从起点到当前格子的耗费
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* 这儿只是简单地把从起点到当前格子需要走几步作为耗费
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* 比较复杂的情况下，可能还需要考虑不同的路面耗费也会不同，
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* 比如沼泽地的耗费比平地要多。不过现在的版本中路况没有这么复杂，
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* 先不考虑。
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*/
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v = this.distance;
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valid_neighbors.push(nb);
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} else {
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// 不可通过或有建筑挡着
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v = -1;
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}
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this.setVal(x, y, v);
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if (x == this.x2 && y == this.y2) {
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this.arrive();
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return false;
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}
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}
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if (valid_neighbors.length == 0) {
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this.blocked();
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return false
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}
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this.current = valid_neighbors;
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return true;
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}
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};
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}); // _TD.a.push end
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