D3DMFOGMODE
This enumeration provides values that identify fog equations used in various render states. Both vertex and pixel fog modes support all of these fog equations.
 D3DMFOG_NONE

Identifies that fogging modes are disabled.
 D3DMFOG_EXP

Identifies a fog model where the fog effect,
F
, intensifies according to the following equation.F = 1/e^(d*density)
In this equation,
e
is the base of the natural logarithm, andd
is distance. The value fordensity
is the value of the D3DMRS_FOGDENSITY render state. For more information, see D3DMRENDERSTATETYPE.
 D3DMFOG_EXP2

Identifies a fog model where the fog effect,
F
, intensifies according to the following equation.F = 1/e^(d*density)<SUP>2</SUP>
 D3DMFOG_LINEAR

Identifies a fog model where the fog effect,
F
, intensifies linearly between the start and end points according to the following equation.F = (end  d)/(end  start)
The values for
start
andend
are the values of the D3DMRS_FOGSTART and D3DMRS_FOGEND render states.
 D3DMFOG_FORCE_ULONG

Forces the compiler to interpret the enumeration as a ULONG value. This value is not used directly in Direct3D Mobile programming.