.overlay

1，在引用.overlay文件中的定義的layout 或者 layoutElement的時候要注意大小寫。

2， //   註釋難道要寫在空行裏

初始化.overlay文件失敗時，要注意在調用initialiseAllResourceGroups()的位置，是否在setDefaultNumMipmaps()的後面

Before we initialize the resources, we should also set the default number of mipmaps that textures use. We must set that before we initialize the resources for it to have any effect.

Add the following code to BasicTutorial6::go:

// Set default mipmap level (NB some APIs ignore this)
Ogre::TextureManager::getSingleton().setDefaultNumMipmaps(5);
// initialise all resource groups
Ogre::ResourceGroupManager::getSingleton().initialiseAllResourceGroups();

The application now has all resource groups initialized and ready to be used.