update

src/EcsGraph.cs

@@ -77,7 +77,7 @@ namespace DCFApixels.DragonECS
         }
         #endregion
 
-        #region New
+        #region New/Convert
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public int NewRelation(int startEntityID, int endEntityID)
         {
@@ -96,19 +96,54 @@ namespace DCFApixels.DragonECS
         private int NewRelationInternal(int startEntityID, int endEntityID)
         {
             int relEntityID = _graphWorld.NewEntity();
+            ConvertToRelationInternal(relEntityID, startEntityID, endEntityID);
+            return relEntityID;
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void ConvertToRelation(int entityID, int startEntityID, int endEntityID)
+        {
+            if (IsRelation(entityID))
+            {
+                Throw.UndefinedException();
+            }
+            ConvertToRelationInternal(entityID, startEntityID, endEntityID);
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void ConvertToRelationInternal(int relEntityID, int startEntityID, int endEntityID)
+        {
             _matrix.Add(startEntityID, endEntityID, relEntityID);
             _relEntityInfos[relEntityID] = new RelationInfo(startEntityID, endEntityID);
             _count++;
-            return relEntityID;
         }
         #endregion
 
-        #region Has
+        #region Inverse
+        public int GetInverseRelation(int relEntityID)
+        {
+            if (relEntityID <= 0 || relEntityID >= _relEntityInfos.Length)
+            {
+                Throw.UndefinedException();
+            }
+            var x = _relEntityInfos[relEntityID];
+            return GetOrNewRelation(x.end, x.start);
+        }
+        #endregion
+
+        #region Has/Is
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool HasRelation(int startEntityID, int endEntityID)
         {
             return _matrix.HasKey(startEntityID, endEntityID);
         }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool IsRelation(int relEntityID)
+        {
+            if (relEntityID <= 0 || relEntityID >= _relEntityInfos.Length)
+            {
+                return false;
+            }
+            return !_relEntityInfos[relEntityID].IsNull;
+        }
         #endregion
 
         #region Get
@@ -133,7 +168,7 @@ namespace DCFApixels.DragonECS
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void ClearRelation_Internal(int relEntityID)
+        internal void ClearRelation_Internal(int relEntityID)
         {
             ref RelationInfo info = ref _relEntityInfos[relEntityID];
             if (_matrix.TryDel(info.start, info.end))
@@ -145,15 +180,7 @@ namespace DCFApixels.DragonECS
         #endregion
 
         #region ArcEntityInfo
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public bool IsRelation(int relEntityID)
-        {
-            if (relEntityID <= 0 || relEntityID >= _relEntityInfos.Length)
-            {
-                return false;
-            }
-            return !_relEntityInfos[relEntityID].IsNull;
-        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public StartEnd GetRelationStartEnd(int relEntityID)
         {

src/EcsGraph.cs.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: 8bbdbeffc4dbc37478284bfc4d2c8d59
+guid: 3beb57467f719d140a946d35ecc5ea89
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2

src/EcsGraphExtensions.cs.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: 1ebb7cb8c3ca3e74dbcec878a032442e
+guid: 977f5bbe4e8bc404bba34ac573f110f2
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2

src/Executors/EcsJoinToSubGraphExecutor.cs

@@ -50,6 +50,11 @@ namespace DCFApixels.DragonECS
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get { return _lastWorldVersion; }
         }
+        public EcsGraph Graph
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get { return _graph; }
+        }
         #endregion
 
         #region OnInitialize/OnDestroy
@@ -210,7 +215,7 @@ namespace DCFApixels.DragonECS
         }
         #endregion
     }
-    
+
     public enum EcsSubGraphMode
     {
         NONE = 0,
@@ -293,10 +298,14 @@ namespace DCFApixels.DragonECS
     {
         private readonly EcsJoinToSubGraphExecutor _executer;
         private readonly EcsSpan _startEntities;
-        public EcsSpan StartEntitiesSpan
+        public EcsSpan FromEntitiesSpan
         {
             get { return _startEntities; }
         }
+        public EcsGraph Graph
+        {
+            get { return _executer.Graph; }
+        }
         internal EcsSubGraph(EcsJoinToSubGraphExecutor executer, EcsSpan startEntites)
         {
             _executer = executer;

src/Executors/EcsJoinToSubGraphExecutor.cs.meta

@@ -1,5 +1,5 @@
 fileFormatVersion: 2
-guid: 37a368fc468a4f845ba8f0426d44ac46
+guid: e335dc14566ec42419fc26638072e636
 MonoImporter:
   externalObjects: {}
   serializedVersion: 2

src/Internal/SparseMatrix.cs

@@ -332,7 +332,7 @@ namespace DCFApixels.DragonECS.Graphs.Internal
                 this.yHash = yHash;
             }
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public static Key FromXY(int x, int y) 
+            public static Key FromXY(int x, int y)
             {
                 unchecked
                 {