Fog blending refers to the application of the fog factor to the fog and object colors to produce the final color that appears in a scene, as discussed in Fog Formulas. The D3DRS_FOGENABLE render state controls fog blending. Set this render state to 1 to enable fog blending as shown in the following example code. The default is 0.

'
' For this example, d3dDevice contains a valid
' reference to a Direct3DDevice8 object.
'
On Local Error Resume Next

Call d3dDevice.SetRenderState(D3DRS_FOGENABLE, 1)
                     
If Err.Number <> D3D_OK Then
    ' Code to handle error goes here.
End If