IDirect3DViewport Interface Method Groups
Applications use the methods of the IDirect3DViewport interface to retrieve and set the properties of viewports. The methods can be organized into the following groups:
Backgrounds GetBackground
Initialization Initialize
IUnknown AddRef
Lights AddLight
Materials and viewports Clear
Transformation TransformVertices
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 Direct3DViewport object without affecting the functionality of the original interface.