diff --git a/source/external/rhino.importer.js b/source/external/rhino.importer.js
index f03791f..9d84c73 100644
--- a/source/external/rhino.importer.js
+++ b/source/external/rhino.importer.js
@@ -4,16 +4,8 @@ OV.Importer3dm = class extends OV.ImporterBase
     {
         super ();
 		this.rhino = null;
-		this.instanceObjects = null;
-		this.instanceDefinitions = null;
     }
-    
-    ResetState ()
-    {
-		this.instanceObjects = {};
-		this.instanceDefinitions = {};
-    }
-
+	
     CanImportExtension (extension)
     {
         return extension === '3dm';
@@ -31,6 +23,18 @@ OV.Importer3dm = class extends OV.ImporterBase
         return OV.Direction.Z;
     }
 
+	ClearContent ()
+	{
+		this.instanceObjects = null;
+		this.instanceDefinitions = null;
+	}
+
+    ResetContent ()
+    {
+		this.instanceObjects = {};
+		this.instanceDefinitions = {};
+    }
+
     ImportContent (fileContent, onFinish)
     {
 		if (this.rhino === null) {
diff --git a/source/import/importer3ds.js b/source/import/importer3ds.js
index 3ebeff5..2ea3236 100644
--- a/source/import/importer3ds.js
+++ b/source/import/importer3ds.js
@@ -49,21 +49,6 @@ OV.Importer3ds = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-
-        this.materialNameToIndex = null;
-        this.meshNameToIndex = null;
-    
-        this.meshTransformations = null;
-        this.defaultMaterialIndex = null;
-    }
-    
-    ResetState ()
-    {
-        this.materialNameToIndex = {};
-        this.meshNameToIndex = {};
-
-        this.meshTransformations = [];
-        this.defaultMaterialIndex = null;
     }
 
     CanImportExtension (extension)
@@ -81,6 +66,24 @@ OV.Importer3ds = class extends OV.ImporterBase
     GetUpDirection ()
     {
         return OV.Direction.Z;
+    }    
+
+    ClearContent ()
+    {
+        this.materialNameToIndex = null;
+        this.meshNameToIndex = null;
+    
+        this.meshTransformations = null;
+        this.defaultMaterialIndex = null;
+    }
+
+    ResetContent ()
+    {
+        this.materialNameToIndex = {};
+        this.meshNameToIndex = {};
+
+        this.meshTransformations = [];
+        this.defaultMaterialIndex = null;
     }
 
     ImportContent (fileContent, onFinish)
diff --git a/source/import/importerbase.js b/source/import/importerbase.js
index debaa14..01e2371 100644
--- a/source/import/importerbase.js
+++ b/source/import/importerbase.js
@@ -2,15 +2,13 @@ OV.ImporterBase = class
 {
     constructor ()
     {
-        this.extension = null;
-        this.callbacks = null;
-        this.model = null;
-        this.error = null;
-        this.message = null;
+        
     }
     
     Import (content, extension, callbacks)
     {
+        this.Clear ();
+
         this.extension = extension;
         this.callbacks = callbacks;
         this.model = new OV.Model ();
@@ -18,12 +16,22 @@ OV.ImporterBase = class
         this.message = null;
 
         let obj = this;
-        obj.ResetState ();
-        obj.ImportContent (content, function () {
+        this.ResetContent ();
+        this.ImportContent (content, function () {
             obj.CreateResult (callbacks);
         });
     }
 
+    Clear ()
+    {
+        this.extension = null;
+        this.callbacks = null;
+        this.model = null;
+        this.error = null;
+        this.message = null;
+        this.ClearContent ();
+    }
+
     CreateResult (callbacks)
     {
         if (this.error) {
@@ -41,11 +49,6 @@ OV.ImporterBase = class
         callbacks.onSuccess ();
     }
 
-    ResetState ()
-    {
-
-    }
-
     CanImportExtension (extension)
     {
         return false;
@@ -61,6 +64,16 @@ OV.ImporterBase = class
         return OV.Direction.Z;
     }
 
+    ClearContent ()
+    {
+
+    }
+
+    ResetContent ()
+    {
+
+    }
+
     ImportContent (fileContent, onFinish)
     {
 
diff --git a/source/import/importergltf.js b/source/import/importergltf.js
index e2ed638..cb975f6 100644
--- a/source/import/importergltf.js
+++ b/source/import/importergltf.js
@@ -348,17 +348,6 @@ OV.ImporterGltf = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-        
-        this.bufferContents = null;
-        this.gltfExtensions = null;
-        this.imageIndexToTextureParams = null;
-    }
-    
-    ResetState ()
-    {
-        this.bufferContents = [];
-        this.gltfExtensions = new OV.GltfExtensions ();
-        this.imageIndexToTextureParams = {};
     }
 
     CanImportExtension (extension)
@@ -380,6 +369,20 @@ OV.ImporterGltf = class extends OV.ImporterBase
         return OV.Direction.Y;
     }
     
+    ClearContent ()
+    {
+        this.bufferContents = null;
+        this.gltfExtensions = null;
+        this.imageIndexToTextureParams = null;
+    }
+
+    ResetContent ()
+    {
+        this.bufferContents = [];
+        this.gltfExtensions = new OV.GltfExtensions ();
+        this.imageIndexToTextureParams = {};
+    }
+
     ImportContent (fileContent, onFinish)
     {
         if (this.extension === 'gltf') {
diff --git a/source/import/importerobj.js b/source/import/importerobj.js
index 198bc28..c0ab107 100644
--- a/source/import/importerobj.js
+++ b/source/import/importerobj.js
@@ -3,33 +3,6 @@ OV.ImporterObj = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-
-        this.globalVertices = null;
-        this.globalNormals = null;
-        this.globalUvs = null;
-    
-        this.currentMesh = null;
-        this.currentMeshData = null;
-        this.currentMaterial = null;
-        this.currentMaterialIndex = null;
-    
-        this.meshNameToMeshData = null;
-        this.materialNameToIndex = null;
-    }
-    
-    ResetState ()
-    {
-        this.globalVertices = [];
-        this.globalNormals = [];
-        this.globalUvs = [];
-
-        this.currentMesh = null;
-        this.currentMeshData = null;
-        this.currentMaterial = null;
-        this.currentMaterialIndex = null;        
-
-        this.meshNameToMeshData = {};
-        this.materialNameToIndex = {};
     }
 
     CanImportExtension (extension)
@@ -50,6 +23,36 @@ OV.ImporterObj = class extends OV.ImporterBase
         return OV.Direction.Y;
     }
     
+    ClearContent ()
+    {
+        this.globalVertices = null;
+        this.globalNormals = null;
+        this.globalUvs = null;
+    
+        this.currentMesh = null;
+        this.currentMeshData = null;
+        this.currentMaterial = null;
+        this.currentMaterialIndex = null;
+    
+        this.meshNameToMeshData = null;
+        this.materialNameToIndex = null;
+    }
+
+    ResetContent ()
+    {
+        this.globalVertices = [];
+        this.globalNormals = [];
+        this.globalUvs = [];
+
+        this.currentMesh = null;
+        this.currentMeshData = null;
+        this.currentMaterial = null;
+        this.currentMaterialIndex = null;        
+
+        this.meshNameToMeshData = {};
+        this.materialNameToIndex = {};
+    }
+    
     ImportContent (fileContent, onFinish)
     {
         let obj = this;
diff --git a/source/import/importeroff.js b/source/import/importeroff.js
index 2cbadb9..30dbef4 100644
--- a/source/import/importeroff.js
+++ b/source/import/importeroff.js
@@ -3,23 +3,8 @@ OV.ImporterOff = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-        this.model = null;
-        this.mesh = null;
-        this.status = null;
     }
     
-    ResetState ()
-    {
-        this.mesh = new OV.Mesh ();
-        this.model.AddMesh (this.mesh);
-        this.status = {
-            vertexCount : 0,
-            faceCount : 0,
-            foundVertex : 0,
-            foundFace : 0
-        };
-    }
-
     CanImportExtension (extension)
     {
         return extension === 'off';
@@ -36,6 +21,25 @@ OV.ImporterOff = class extends OV.ImporterBase
     {
         return OV.Direction.Y;
     }
+    
+    ClearContent ()
+    {
+        this.model = null;
+        this.mesh = null;
+        this.status = null;
+    }
+
+    ResetContent ()
+    {
+        this.mesh = new OV.Mesh ();
+        this.model.AddMesh (this.mesh);
+        this.status = {
+            vertexCount : 0,
+            faceCount : 0,
+            foundVertex : 0,
+            foundFace : 0
+        };
+    }
 
     ImportContent (fileContent, onFinish)
     {
diff --git a/source/import/importerply.js b/source/import/importerply.js
index afeae6a..4de747c 100644
--- a/source/import/importerply.js
+++ b/source/import/importerply.js
@@ -89,16 +89,8 @@ OV.ImporterPly = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-        this.model = null;
-        this.mesh = null;
     }
     
-    ResetState ()
-    {
-        this.mesh = new OV.Mesh ();
-        this.model.AddMesh (this.mesh);
-    }
-
     CanImportExtension (extension)
     {
         return extension === 'ply';
@@ -115,6 +107,18 @@ OV.ImporterPly = class extends OV.ImporterBase
     {
         return OV.Direction.Y;
     }
+    
+    ClearContent ()
+    {
+        this.model = null;
+        this.mesh = null;
+    }
+
+    ResetContent ()
+    {
+        this.mesh = new OV.Mesh ();
+        this.model.AddMesh (this.mesh);
+    }
 
     ImportContent (fileContent, onFinish)
     {
diff --git a/source/import/importerstl.js b/source/import/importerstl.js
index bea4d72..0141a71 100644
--- a/source/import/importerstl.js
+++ b/source/import/importerstl.js
@@ -3,15 +3,6 @@ OV.ImporterStl = class extends OV.ImporterBase
     constructor ()
     {
         super ();
-        this.mesh = null;
-        this.triangle = null;
-    }
-    
-    ResetState ()
-    {
-        this.mesh = new OV.Mesh ();
-        this.model.AddMesh (this.mesh);
-        this.triangle = null;
     }
 
     CanImportExtension (extension)
@@ -29,6 +20,19 @@ OV.ImporterStl = class extends OV.ImporterBase
     GetUpDirection ()
     {
         return OV.Direction.Z;
+    }    
+    
+    ClearContent ()
+    {
+        this.mesh = null;
+        this.triangle = null;
+    }
+
+    ResetContent ()
+    {
+        this.mesh = new OV.Mesh ();
+        this.model.AddMesh (this.mesh);
+        this.triangle = null;
     }
 
     ImportContent (fileContent, onFinish)