IDirect3D Interface Method Groups
Applications use the methods of the IDirect3D interface to create Direct3D objects and set up the environment. The methods can be organized into the following groups:
Creation CreateLight
Enumeration EnumDevices
and initialization FindDevice
IUnknown AddRef
All COM interfaces inherit the IUnknown interface methods, which are listed in the "IUnknown" group above. These three methods allow additional interfaces to be added to the Direct3D object without affecting the functionality of the original interface.