Hi everyone , I want to acquire vertex buffer's data, and copy the data to new model. I try to use GetPrivateData, but I cant understand what is 1st param - const GUID& ? How can I know the data's guid ?

GetPrivateData is not the call you're looking for - it's not used for this kind of operation at all. Depending on the buffer's usage and CPU access flags, you can use one of Map or CopyResource to do this.

Thank you ! That's the answer I really waiting for ! But what data dus GetPrivateData() truely acquire ?

http://msdn.microsoft.com/en-us/library/windows/desktop/ff476380%28v=vs.85%29.aspx

Basically, Get/Set PrivateData is so you can associate application-specific data to the object, e.g. set a "friendly" name to it for debugging purposes.

Really thank you for your help