title: Parallax effect on tile map layers
body: <p>i am using three layers of tiled map and i want to give parallax effect on these layers.
  my code is:</p>
  
  <pre><code>     CCTMXTiledMap *city = CCTMXTiledMap::create("City.tmx");
  
       CCTMXLayer* ForegroundLayer = city-&gt;layerNamed("ForeGround");
   CCTMXLayer* BackgroundLayer1 = city-&gt;layerNamed("Background1");
   CCTMXLayer* BackgroundLayer2 = city-&gt;layerNamed("Background2");
  
       CCParallaxNode* voidNode = CCParallaxNode::create();
  
      // NOW add the 3 layers to the 'void' node
  
       voidNode-&gt;addChild(BackgroundLayer2, -1, ccp(0.4f,0.5f), CCPointZero);
       voidNode-&gt;addChild(BackgroundLayer1, 1, ccp(2.2f,1.0f), ccp(0,-200) );
       voidNode-&gt;addChild(ForegroundLayer, 2, ccp(3.0f,2.5f), ccp(200,800) );
  
  voidNode-&gt;runAction(temp); //some action temp
  
      addChild(voidNode);
  </code></pre>
  
  <p>It gives  assertion failed: child->m_pParent==0
  Same code works if we use sprites instead of TMXLayers.
  what I have done wrong in this code?</p>