http://www.hightopo.com/demo/astar/astar.html
最近搞个游戏遇到最短路径的常规游戏问题，一时起兴基于HT for Web写了个A*算法的WebGL 3D呈现，算法基于开源 https://github.com/bgrins/javascript-astar 的javascript实现，其实作者也有个不错的2D例子实现 http://www.briangrinstead.com/files/astar/ ，只不过觉得所有A*算法的可视化实现都是平面的不够酷，另外还有不少参数需要调节控制，还是值得好好搞个全面的Demo，先上张2D和3D例子的对照图。
实现代码比较容易一百多行，不过算法核心在astar.js了，界面核心在ht.js里面了，我只需要构建网格信息，只需监听用户点击，然后调用astar.js进行最短路径计算，将结果通过动画的方式呈现出走动的过程，所有代码如下：
function init() {
w = 40; m = 20; d = w * m / 2;
gridRows = [];
dm = new ht.DataModel();
g3d = new ht.graph3d.Graph3dView(dm);
g3d.setGridVisible(true);
g3d.setGridColor('#BBBBBB');
g3d.setGridSize(m);
g3d.setGridGap(w);
g3d.addToDOM();
g3d.sm().setSelectionMode('none');
anim = startBall = endBall = null;
g3d.getView().addEventListener(ht.Default.isTouchable ? 'touchstart' : 'mousedown', function(e){
if(!anim){
var p = g3d.getHitPosition(e);
var x = Math.floor((p[0] + d)/ w);
var y = Math.floor((p[2] + d)/ w);
var endBall = dm.getDataByTag("cell_" + x + "_" + y);
if(endBall && endBall.s('batch') !== 'wall'){
if(startBall.a('x') === x && startBall.a('y') === y){
return;
}
var g = new Graph(gridRows, {
diagonal: formPane.v('diagonal')
});
var start = g.grid[startBall.a('x')][startBall.a('y')];
var end = g.grid[x][y];
var result = astar.search(g, start, end, {
closest: formPane.v('closest')
});
if(!result.length){
return;
}
x = result[result.length-1].x;
y = result[result.length-1].y;
endBall = dm.getDataByTag("cell_" + x + "_" + y);
endBall.s('3d.visible', true);
startBall.s('3d.visible', false);
formPane.setDisabled(true);
anim = ht.Default.startAnim({
duration: 700,
finishFunc: function(){
for(var i=0; i<result.length; i++){
var ball = dm.getDataByTag("cell_" + result[i].x + "_" + result[i].y);
ball.s({
'3d.visible': false,
'shape3d.opacity': 1,
'shape3d.transparent': false
});
startBall.p3(-d+w*x+w/2, w/2, -d+w*y+w/2);
startBall.a({x: x, y: y});
startBall.s('3d.visible', true);
}
anim = null;
formPane.setDisabled(false);
},
action: function(v){
var index = Math.round(v*result.length);
for(var i=0; i<index; i++){
var ball = dm.getDataByTag("cell_" + result[i].x + "_" + result[i].y);
ball.s({
'3d.visible': true,
'shape3d.opacity': i/index*0.3 + 0.7,
'shape3d.transparent': true
});
}
}
});
}
}
}, false);
createFormPane();
createGrid();
}
function createGrid(){
dm.clear();
var ball;
gridRows.length = 0;
for(var x = 0; x < m; x++) {
var nodeRow = [];
gridRows.push(nodeRow);
for(var y = 0; y < m; y++) {
var isWall = Math.floor(Math.random()*(1/formPane.v('frequency')));
if(isWall === 0){
nodeRow.push(0);
createNode(x, y).s({
'batch': 'wall',
'all.color': '#9CA69D'
});
}else{
nodeRow.push(1);
ball = createNode(x, y).s({
'shape3d': 'sphere',
'shape3d.color': '#FF703F',
'3d.visible': false
});
}
}
}
if(!ball){
createGrid();
return;
}
startBall = createNode(ball.a('x'), ball.a('y'), 'start').s({
'shape3d': 'sphere',
'shape3d.color': '#FF703F'
});
shape = new ht.Shape();
shape.setPoints(new ht.List([
{x: -d, y: d},
{x: d, y: d},
{x: d, y: -d},
{x: -d, y: -d},
{x: -d, y: d}
]));
shape.setThickness(4);
shape.setTall(w);
shape.setElevation(w/2);
shape.setClosePath(true);
shape.s({
'all.color': 'rgba(187, 187, 187, 0.8)',
'all.transparent': true,
'all.reverse.cull': true
});
dm.add(shape);
}
function createNode(x, y, tag){
var node = new ht.Node();
tag = tag || "cell_" + x + "_" + y;
node.setTag(tag);
node.a({ x: x, y: y });
node.s3(w*0.9, w*0.9, w*0.9);
node.p3(-d+w*x+w/2, w/2, -d+w*y+w/2);
node.s({
'all.reverse.cull': true,
'shape3d.reverse.cull': true
});
dm.add(node);
return node;
}
function createFormPane() {
formPane = new ht.widget.FormPane();
formPane.setWidth(230);
formPane.setHeight(70);
formPane.getView().className = 'formpane';
document.body.appendChild(formPane.getView());
formPane.addRow(['Wall Frequency', {
id: 'frequency',
slider: {
min: 0,
max: 0.8,
value: 0.1,
onValueChanged: function(){
createGrid();
}
}
}], [100, 0.1]);
formPane.addRow([
{
id: 'closest',
checkBox: {
label: 'Try Closest'
}
},
{
id: 'diagonal',
checkBox: {
label: 'Allow Diagonal'
}
}
], [0.1, 0.1]);
}
只从iOS8支持WebGL后在移动终端上测试3D应用比当前的大部分Android平板舒服多了，以上的例子在iOS系统下呈现和算法都挺流畅，http://v.youku.com/v_show/id_XODMzOTU1Njcy.html，当然这个小例子数据量也不大，本质其实还是2D的最短路径算法，并非真正意义的3D空间最短路径，但还是足够解决很多实际应用问题了。
http://www.hightopo.com/demo/astar/astar.html
