After attaching the depth buffer to the render-target surface, you can create a rendering device from the render target. Given a rendering device, you enable depth buffering by setting the D3DRENDERSTATE_ZENABLE render state for the device. The D3DZBUFFERTYPE enumerated type includes members to set the depth-buffer render state. The D3DZB_TRUE member (or TRUE) enables z-buffering. The ZBuffer sample enables z-buffering during scene rendering in the App_Render application-defined function. The following is the appropriate excerpt from App_Render:
// Enable z-buffering.
pd3dDevice->SetRenderState( D3DRENDERSTATE_ZENABLE, TRUE );
Although this tutorial enables depth-buffering each frame, it is not necessary to do so. A real-world application would likely set the D3DRENDERSTATE_ZENABLE render state during scene initialization, only changing to disable depth buffering or to choose another type of depth buffering.
Note The D3DZBUFFERTYPE enumerated type includes the D3DZB_USEW value to enable w-based depth comparisons on compliant hardware. For more information, see Depth Buffers.