D3DRMFOGMODE

typedef enum _D3DRMFOGMODE{

D3DRMFOG_LINEAR,

D3DRMFOG_EXPONENTIAL,

D3DRMFOG_EXPONENTIALSQUARED

} D3DRMFOGMODE;

Contains values that specify how rapidly and in what ways the fog effect intensifies with increasing distance from the camera.

D3DRMFOG_LINEAR

The fog effect intensifies linearly between the start and end points, according to the following formula:

This is the only fog mode supported for DirectX 2.

D3DRMFOG_EXPONENTIAL

The fog effect intensifies exponentially, according to the following formula:

D3DRMFOG_EXPONENTIALSQUARED

The fog effect intensifies exponentially with the square of the distance, according to the following formula:

Note that fog can be considered a measure of visibility—the lower the fog value produced by one of the fog equations, the less visible an object is.

You can specify the fog's density and start and end points by using the IDirect3DRMFrame::SetSceneFogParams method. In the formulas for the exponential fog modes, e is the base of the natural logarithms; its value is approximately 2.71828.