Hardware Abstraction and Emulation

The Direct3D API (like the rest of the DirectX API) is built on top of a hardware-abstraction layer (HAL), which insulates you from device-specific dependencies present in the hardware. A companion piece to the Direct3D HAL is the hardware-emulation layer (HEL). The Direct3D HEL provides software-based emulation of features that are not present in hardware. The combination of these hardware abstraction and emulation layers ensures that the services of the API are always available to you.

The Direct3D HAL is tightly integrated with the DirectDraw HAL and the GDI display driver, giving hardware manufacturers a single, consistent interface to Microsoft graphics APIs, and a long-term, unified driver model for accelerated 3D. Hardware manufacturers need to write only a single driver to accelerate Direct3D, DirectDraw, GDI, and OpenGL. Hardware can accelerate all or part of the 3D graphics rendering pipeline, including geometry transformations, 3D clipping and lighting, and rasterization. The Direct3D HAL has been designed to accommodate future graphics accelerators in addition to those available today.