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1 Array.prototype.each = function(f) { | |
2 if(!f.apply) return; | |
3 for(var i=0;i<this.length;i++) { | |
4 f.apply(this[i], [i, this]); | |
5 } | |
6 } | |
7 Array.prototype.findGraphNode = function(obj) { | |
8 for(var i=0;i<this.length;i++) { | |
9 if(this[i].pos == obj.pos) { return this[i]; } | |
10 } | |
11 return false; | |
12 }; | |
13 Array.prototype.removeGraphNode = function(obj) { | |
14 for(var i=0;i<this.length;i++) { | |
15 if(this[i].pos == obj.pos) { this.splice(i,1); } | |
16 } | |
17 return false; | |
18 }; | |
19 | |
20 function createGraphSet(gridSize, wallFrequency) { | |
21 var graphSet = []; | |
22 for(var x=0;x<gridSize;x++) { | |
23 var row = []; | |
24 for(var y=0;y<gridSize;y++) { | |
25 // maybe set this node to be wall | |
26 var rand = Math.floor(Math.random()*(1/wallFrequency)); | |
27 row.push(new GraphNode(x,y,(rand == 0))); | |
28 } | |
29 graphSet.push(row); | |
30 } | |
31 return graphSet; | |
32 } | |
33 | |
34 // astar.js | |
35 // Implements the astar search algorithm in javascript | |
36 | |
37 var astar = { | |
38 init: function(grid) { | |
39 for(var x = 0; x < grid.length; x++) { | |
40 for(var y = 0; y < grid[x].length; y++) { | |
41 grid[x][y].f = 0; | |
42 grid[x][y].g = 0; | |
43 grid[x][y].h = 0; | |
44 grid[x][y].parent = null; | |
45 } | |
46 } | |
47 }, | |
48 search: function(grid, start, end) { | |
49 astar.init(grid); | |
50 | |
51 var openList = []; | |
52 var closedList = []; | |
53 openList.push(start); | |
54 | |
55 while(openList.length > 0) { | |
56 | |
57 // Grab the lowest f(x) to process next | |
58 var lowInd = 0; | |
59 for(var i=0; i<openList.length; i++) { | |
60 if(openList[i].f < openList[lowInd].f) { lowInd = i; } | |
61 } | |
62 var currentNode = openList[lowInd]; | |
63 | |
64 // End case -- result has been found, return the traced path | |
65 if(currentNode.pos == end.pos) { | |
66 var curr = currentNode; | |
67 var ret = []; | |
68 while(curr.parent) { | |
69 ret.push(curr); | |
70 curr = curr.parent; | |
71 } | |
72 return ret.reverse(); | |
73 } | |
74 | |
75 // Normal case -- move currentNode from open to closed, process each
of its neighbors | |
76 openList.removeGraphNode(currentNode); | |
77 closedList.push(currentNode); | |
78 var neighbors = astar.neighbors(grid, currentNode); | |
79 | |
80 for(var j=0; j<neighbors.length;j++) { | |
81 var neighbor = neighbors[j]; | |
82 if(closedList.findGraphNode(neighbor) || neighbor.isWall()) { | |
83 // not a valid node to process, skip to next neighbor | |
84 continue; | |
85 } | |
86 | |
87 // g score is the shortest distance from start to current node,
we need to check if | |
88 // the path we have arrived at this neighbor is the shortest o
ne we have seen yet | |
89 var gScore = currentNode.g + 1; // 1 is the distance from a node
to it's neighbor | |
90 var gScoreIsBest = false; | |
91 | |
92 | |
93 if(!openList.findGraphNode(neighbor)) { | |
94 // This the the first time we have arrived at this node, it
must be the best | |
95 // Also, we need to take the h (heuristic) score since we ha
ven't done so yet | |
96 | |
97 gScoreIsBest = true; | |
98 neighbor.h = astar.heuristic(neighbor.pos, end.pos); | |
99 openList.push(neighbor); | |
100 } | |
101 else if(gScore < neighbor.g) { | |
102 // We have already seen the node, but last time it had a wor
se g (distance from start) | |
103 gScoreIsBest = true; | |
104 } | |
105 | |
106 if(gScoreIsBest) { | |
107 // Found an optimal (so far) path to this node. Store info
on how we got here and | |
108 // just how good it really is... | |
109 neighbor.parent = currentNode; | |
110 neighbor.g = gScore; | |
111 neighbor.f = neighbor.g + neighbor.h; | |
112 } | |
113 } | |
114 } | |
115 | |
116 // No result was found -- empty array signifies failure to find path | |
117 return []; | |
118 }, | |
119 heuristic: function(pos0, pos1) { | |
120 // This is the Manhattan distance | |
121 var d1 = Math.abs (pos1.x - pos0.x); | |
122 var d2 = Math.abs (pos1.y - pos0.y); | |
123 return d1 + d2; | |
124 }, | |
125 neighbors: function(grid, node) { | |
126 var ret = []; | |
127 var x = node.pos.x; | |
128 var y = node.pos.y; | |
129 | |
130 if(grid[x-1] && grid[x-1][y]) { | |
131 ret.push(grid[x-1][y]); | |
132 } | |
133 if(grid[x+1] && grid[x+1][y]) { | |
134 ret.push(grid[x+1][y]); | |
135 } | |
136 if(grid[x][y-1] && grid[x][y-1]) { | |
137 ret.push(grid[x][y-1]); | |
138 } | |
139 if(grid[x][y+1] && grid[x][y+1]) { | |
140 ret.push(grid[x][y+1]); | |
141 } | |
142 return ret; | |
143 } | |
144 }; | |
145 | |
146 function go() { | |
147 path = astar.search(g1, start, end); | |
148 }; | |
149 | |
150 go(); | |
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