Direct3D Initialization - Introduction to 3D Game Programming with DirectX 9.0 - page 55

return true;

}

void Cleanup()
{

}
We don't have any resources or things to set up in this sample, so the
Setup and Cleanup methods are empty.
bool Display(float timeDelta)
{

if( Device )
{

Device->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER,
0x00000000, 1.0f, 0);

Device->Present(0, 0, 0, 0);// present backbuffer

}
return true;

}
The Display method calls the IDirect3DDevice9::Clear
method, which clears the back buffer and depth/stencil buffer to the
color black and 1.0, respectively. Notice that we only perform the draw-
ing code if the application is not paused. The declaration of
IDirect3DDevice9::Clear is:
HRESULT IDirect3DDevice9::Clear(
DWORD Count,
const D3DRECT* pRects,
DWORD Flags,
D3DCOLOR Color,
float Z,
DWORD Stencil

);

Count —Number of rectangles in the pRects array

pRects —An array of screen rectangles to clear. This allows us to
only clear parts of a surface.

Flags —Specifies which surfaces to clear. We can clear one or
more of the following surfaces:
D3DCLEAR_TARGET —The render target surface, usually the
back buffer
D3DCLEAR_ZBUFFER —The depth buffer
D3DCLEAR_STENCIL —The stencil buffer

Color —The color we wish to clear the render target to

Z —The value we wish to set the depth buffer (z-buffer) to

Stencil —The value we wish to set the stencil buffer to