基于HT for Web的3D呈现A* Search Algorithm

最近搞个游戏遇到最短路径的常规游戏问题，正巧看到老同事写的3D机房最短路径巡线文章，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。

<iframe src="http://player.youku.com/embed/XODMzOTU1Njcy" frameborder="0" width="510" height="498"></iframe>