Syntax

[C/C++:]
void gDefineFog(int mode, int colour, ...);

[F90:]
subroutine gDefineFog(mode, colour, gStart, gEnd, gDensity) 
integer, intent(in) :: mode,colour

real, optional, intent(in) :: gStart, gEnd, gDensity

Arguments

mode
Fog mode

= GNONE,

No fog

= GLINEAR,

Linear for depth-cueing

= GEXP1,

Exponential for cloud and heavy fog

= GEXP2,

Exponential for smoke and weather haze

colour
Fog  colour (index or 24bit true colour value)

Optional Args

gStart
Start depth for linear fog (default = 0.0)

gEnd
End depth for linear fog (default = 3D viewport Z range)

gDensity
Fog density for exponential modes (default = 0.0025)

Description

The routine gDefineFog() specifies the current fog mode and colour. When switched on, in conjunction with depth buffering (see gSetShadingMode()), objects further away from the viewer are blended into the specified fog colour according to the specified mode.

The optional arguments gStart and gEnd are used for GLINEAR mode, where objects in front of gStart are displayed normally, objects between gStart and gEnd are linearly blended into the fog colour and objects behind gEnd are displayed totally in the fog colour. The default range of values for gStart and gEnd are 0.0 to the 3D viewport Z range which represents the eye-point to the furthest possible distance of the scene.

The GEXP1 and GEXP2 modes represent more realistic atmospheric fog modes, with the former using an exponential function of  - (gDensity * viewing distance)  and the latter using a function of  - (gDensity * viewing distance) squared. Values in the range 0.5 to very small give realistic effects.

See Also

gDefineFog Usage
gSetShadingMode
gSetViewport3D

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