Why Use Direct3D Immediate Mode?

The world management of Immediate Mode is based on vertices, polygons, and commands that control them. It allows immediate access to the transformation, lighting, and rasterization 3-D graphics pipeline. If hardware isn't present to accelerate rendering, Direct3D offers robust software emulation. Developers with existing 3-D applications and developers who need to achieve maximum performance by maintaining the thinnest possible layer between their application and the hardware should use Immediate Mode, instead of Retained Mode.

Direct3D Immediate Mode provides simple and straightforward methods to set up and render a 3-D scene. The key set of rendering methods are referred to as DrawPrimitive methods; they enable applications to render one or more objects in a scene with a single method call. For more information about these methods, see DrawPrimitive Methods.

Immediate Mode allows a low-overhead connection to 3-D hardware. This low-overhead connection comes at a price; you must provide explicit calls for transformations and lighting, you must provide all the necessary matrices, and you must determine what kind of hardware is present and what its capabilities are.