Direct3D Immediate Mode has undergone many changes between DirectX 3 and DirectX 5. One of the benefits of the COM model is that it allows additions and modifications to sets of API elements without breaking existing applications. All of the DirectX 3 interfaces are supported in DirectX 5. The DirectX 3 interfaces also work in a similar way (except for a few bug fixes).
The new functionality in DirectX 5 required the addition of many new interfaces. The most important changes in DirectX 5 have been the addition of the DrawPrimitive methods and the new device object model. For more information about the DrawPrimitive methods, see The DrawPrimitive Methods. For more information about the new device object model, see Objects and Interfaces.