Implement Scene.clone #3032

The object returnen by the scene's clone method is now a fully valid scene and
can be used in rendering.

build/three.js

@@ -14506,6 +14506,25 @@ THREE.Scene.prototype.__removeObject = function ( object ) {
 
 };
 
+THREE.Scene.prototype.clone = function (object) {
+    if ( object === undefined ) object = new THREE.Scene();
+
+    THREE.Object3D.prototype.clone.call(this, object);
+    
+    if(this.fog !== null) {
+        object.fog = this.fog.clone();
+    }
+
+    if(this.overrideMaterial !== null) {
+        object.overrideMaterial = this.overrideMaterial.clone();
+    }
+    
+    object.autoUpdate = this.autoUpdate;
+    object.matrixAutoUpdate = this.matrixAutoUpdate;
+
+    return object;
+};
+
 /**
  * @author mrdoob / http://mrdoob.com/
  * @author alteredq / http://alteredqualia.com/

src/scenes/Scene.js

@@ -109,3 +109,22 @@ THREE.Scene.prototype.__removeObject = function ( object ) {
 	}
 
 };
+
+THREE.Scene.prototype.clone = function (object) {
+    if ( object === undefined ) object = new THREE.Scene();
+
+    THREE.Object3D.prototype.clone.call(this, object);
+    
+    if(this.fog !== null) {
+        object.fog = this.fog.clone();
+    }
+
+    if(this.overrideMaterial !== null) {
+        object.overrideMaterial = this.overrideMaterial.clone();
+    }
+    
+    object.autoUpdate = this.autoUpdate;
+    object.matrixAutoUpdate = this.matrixAutoUpdate;
+
+    return object;
+};