Microsoft DirectX 8.1 (Visual Basic)

CONST_D3DFOGMODE

Defines constants that describe the fog mode.

Enum CONST_D3DFOGMODE
    D3DFOG_NONE   = 0
    D3DFOG_EXP    = 1
    D3DFOG_EXP2   = 2
    D3DFOG_LINEAR = 3
End Enum

D3DFOG_NONE

No fog effect.

D3DFOG_EXP

Fog effect intensifies exponentially, according to the following formula.

D3DFOG_EXP2

Fog effect intensifies exponentially with the square of the distance, according to the following formula.

D3DFOG_LINEAR

Fog effect intensifies linearly between the start and end points, according to the following formula.

This is the only fog mode currently supported.

These flags are used to set the value of the D3DRS_FOGTABLEMODE and D3DRS_FOGVERTEXMODE render states for the CONST_D3DRENDERSTATETYPE enumeration.

Fog can be considered a measure of visibility—the lower the fog value produced by a fog equation, the less visible an object is.