Architectural Overview of Immediate Mode

Direct3D applications communicate with graphics hardware in a similar fashion whether they use Retained Mode or Immediate Mode. They may or may not take advantage of software emulation before interacting with the hardware emulation layer (HAL). Since Direct3D is an interface to a DirectDraw® object, the HAL is referred to as the DirectDraw/Direct3D HAL.

Direct3D is tightly integrated with the DirectDraw component of DirectX. DirectDraw surfaces are used as rendering targets (front and back surfaces) and as z-buffers. The Direct3D interface is actually an interface to a DirectDraw object.