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Unity3D A* 寻路算法

发表于2017-05-17
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A*算法在游戏领域是最常见的算法，通常是应用于大型网络游戏中，在移动端游戏开发中，A*算法也可以在Unity端实现。下面给大家介绍一个插件A* PathFindingProject，可以直接导入到Unity工程中，它目前支持直接寻路和网格寻路。再通过一个Demo，给大家详细介绍下。


在导入到Unity工程后，使用时首选建立一个空的GameObject，然后将AstarPath脚本挂接上去。如下图所示：


这个AstarPath是整个A＊寻路的核心组件，它计算了整个地面的寻路路径以及保存信息，它保存的是二进制文件格式，操作如下所示：

该类提供了保存，加载等函数，详情可以查看类AstarPathEditor，函数接口如下所示：

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void DrawSerializationSettings () { 
            serializationSettingsArea.Begin(); 
            GUILayout.BeginHorizontal(); 
   
            if (GUILayout.Button("Save & Load", level0LabelStyle)) { 
                serializationSettingsArea.open = !serializationSettingsArea.open; 
            } 
   
            if (script.data.cacheStartup && script.data.file_cachedStartup != null) { 
                GUIUtilityx.PushTint(Color.yellow); 
                GUILayout.Label("Startup cached", thinHelpBox, GUILayout.Height(15)); 
                GUILayout.Space(20); 
                GUIUtilityx.PopTint(); 
            } 
   
            GUILayout.EndHorizontal(); 
   
            // This displays the serialization settings 
            if (serializationSettingsArea.BeginFade()) { 
                script.data.cacheStartup = EditorGUILayout.Toggle(new GUIContent("Cache startup", "If enabled, will cache the graphs so they don't have to be scanned at startup"), script.data.cacheStartup); 
   
                script.data.file_cachedStartup = EditorGUILayout.ObjectField(script.data.file_cachedStartup, typeof(TextAsset), false) as TextAsset; 
   
                if (script.data.cacheStartup && script.data.file_cachedStartup == null) { 
                    EditorGUILayout.HelpBox("No cache has been generated", MessageType.Error); 
                } 
   
                if (script.data.cacheStartup && script.data.file_cachedStartup != null) { 
                    EditorGUILayout.HelpBox("All graph settings will be replaced with the ones from the cache when the game starts", MessageType.Info); 
                } 
   
                GUILayout.BeginHorizontal(); 
   
                if (GUILayout.Button("Generate cache")) { 
                    var serializationSettings = new Pathfinding.Serialization.SerializeSettings(); 
                    serializationSettings.nodes = true; 
   
                    if (EditorUtility.DisplayDialog("Scan before generating cache?", "Do you want to scan the graphs before saving the cache.n" + 
                            "If the graphs have not been scanned then the cache may not contain node data and then the graphs will have to be scanned at startup anyway.", "Scan", "Don't scan")) { 
                        MenuScan(); 
                    } 
   
                    // Save graphs 
                    var bytes = script.data.SerializeGraphs(serializationSettings); 
   
                    // Store it in a file 
                    script.data.file_cachedStartup = SaveGraphData(bytes, script.data.file_cachedStartup); 
                    script.data.cacheStartup = true; 
                } 
   
                if (GUILayout.Button("Load from cache")) { 
                    if (EditorUtility.DisplayDialog("Are you sure you want to load from cache?", "Are you sure you want to load graphs from the cache, this will replace your current graphs?", "Yes", "Cancel")) { 
                        script.data.LoadFromCache(); 
                    } 
                } 
   
                GUILayout.EndHorizontal(); 
   
                if (script.data.data_cachedStartup != null && script.data.data_cachedStartup.Length > 0) { 
                    EditorGUILayout.HelpBox("Storing the cached starup data on the AstarPath object has been deprecated. It is now stored " + 
                        "in a separate file.", MessageType.Error); 
   
                    if (GUILayout.Button("Transfer cache data to separate file")) { 
                        script.data.file_cachedStartup = SaveGraphData(script.data.data_cachedStartup); 
                        script.data.data_cachedStartup = null; 
                    } 
                } 
   
                GUILayout.Space(5); 
   
                GUILayout.BeginHorizontal(); 
                if (GUILayout.Button("Save to file")) { 
                    string path = EditorUtility.SaveFilePanel("Save Graphs", "", "graph.bytes", "bytes"); 
   
                    if (path != "") { 
                        var serializationSettings = Pathfinding.Serialization.SerializeSettings.Settings; 
                        if (EditorUtility.DisplayDialog("Include node data?", "Do you want to include node data in the save file. " + 
                                "If node data is included the graph can be restored completely without having to scan it first.", "Include node data", "Only settings")) { 
                            serializationSettings.nodes = true; 
                        } 
   
                        if (serializationSettings.nodes && EditorUtility.DisplayDialog("Scan before saving?", "Do you want to scan the graphs before saving? " + 
                                "nNot scanning can cause node data to be omitted from the file if the graph is not yet scanned.", "Scan", "Don't scan")) { 
                            MenuScan(); 
                        } 
   
                        uint checksum; 
                        var bytes = SerializeGraphs(serializationSettings, out checksum); 
                        Pathfinding.Serialization.AstarSerializer.SaveToFile(path, bytes); 
   
                        EditorUtility.DisplayDialog("Done Saving", "Done saving graph data.", "Ok"); 
                    } 
                } 
   
                if (GUILayout.Button("Load from file")) { 
                    string path = EditorUtility.OpenFilePanel("Load Graphs", "", ""); 
   
                    if (path != "") { 
                        byte[] bytes; 
                        try { 
                            bytes = Pathfinding.Serialization.AstarSerializer.LoadFromFile(path); 
                        } catch (System.Exception e) { 
                            Debug.LogError("Could not load from file at '"+path+"'n"+e); 
                            bytes = null; 
                        } 
   
                        if (bytes != null) DeserializeGraphs(bytes); 
                    } 
                } 
   
                GUILayout.EndHorizontal(); 
            } 
   
            serializationSettingsArea.End(); 
        }

该函数调用了JsonSerializer类中的两个函数如下所示：

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public static void SaveToFile (string path, byte[] data) { 
f NETFX_CORE 
    throw new System.NotSupportedException("Cannot save to file on this platform"); 
lse 
    using (var stream = new FileStream(path, FileMode.Create)) { 
        stream.Write(data, 0, data.Length); 
    } 
ndif 
} 
   
/** Load the specified data from the specified path */ 
public static byte[] LoadFromFile (string path) { 
f NETFX_CORE 
    throw new System.NotSupportedException("Cannot load from file on this platform"); 
lse 
    using (var stream = new FileStream(path, FileMode.Open)) { 
        var bytes = new byte[(int)stream.Length]; 
        stream.Read(bytes, 0, (int)stream.Length); 
        return bytes; 
    } 
ndif 
}

场景通过AstarPath脚本布置完后，接下来开始寻路了，需要挂接如下的脚本：


其中AI脚本是用于查询物体的，它会调用Seeker脚本中的函数，同时Seeker会对场景做一些标识操作，这样AI寻路基本完成，其中AI脚本是继承AIPath类，非常方便我们自己编写，扩展功能，它是通过递归的方式进行路径查询，锁定目标的，它运行的效果如下所示：

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游戏开发Unity游戏视觉场景接口寻路算法