基于HT for Web的3D呈现A* Search Algorithm

本文主要是介绍基于HT for Web的3D呈现A* Search Algorithm，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

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。

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