fglFogFuncSGIS(3G) OpenGL Reference fglFogFuncSGIS(3G)NAMEfglFogFuncSGIS - custom fog blending function
FORTRAN SPECIFICATION
SUBROUTINE fglFogFuncSGIS( INTEGER*4 n,
CHARACTER*8 points )
PARAMETERS
n Specifies the number of control points in the custom fog blending
function. The initial value is 1.
points Specifies an array of control points. Each control point
consists of two floating-point values. The first is an eye-space
distance, and the second is a fog blending factor in the range
[0.0,1.0]. Blending factor 0.0 indicates full fog, and 1.0
indicates no fog. The initial value is (0.0,1.0) (no fog).
DESCRIPTIONfglFogFuncSGIS defines the control points for the custom fog blending
function that is applied when the fog mode is GL_FOG_FUNC_SGIS. See
fglFog for a discussion of the various fog modes and the operation of the
custom blending function.
n is the number of control points in the custom fog blending function.
It must not be larger than the value returned by fglGet with argument
GL_MAX_FOG_FUNC_POINTS_SGIS. It must be at least 1.
points is an array of pairs of floating-point values that define the
control points. Each control point consists of an eye-space distance
from the viewpoint (always non-negative) and the corresponding fog
blending factor (in the range [0.0,1.0]). Blending factor 0.0 results in
full fog, and 1.0 results in no fog. The control points must be
specified in order: eye space distance must not decrease from one control
point to the next, and the fog blending factor must not increase from one
control point to the next.
n and points completely specify the custom fog blending function,
replacing any previous specification that may have existed.
NOTES
Note that since each control point is a pair of values, there are 2*n
floating-point values in points.
fglFogFuncSGIS is part of the SGIS_fog_func extension, not part of the
core GL command set. If GL_SGIS_fog_func is included in the string
returned by fglGetString when called with argument GL_EXTENSIONS,
extension SGIS_fog_func is supported by the connection. See fglIntro for
more information about using extensions.
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fglFogFuncSGIS(3G) OpenGL Reference fglFogFuncSGIS(3G)ERRORS
GL_INVALID_VALUE is generated if n is less than 1.
GL_INVALID_VALUE is generated if any eye-space distance in points is
negative, or if any blend factor in points is outside the range
[0.0,1.0].
GL_INVALID_VALUE is generated if the eye-space distance decreases from
one control point to the next, or if the blending factor increases from
one control point to the next.
GL_INVALID_OPERATION is generated if fglFogFuncSGIS is executed between
the execution of fglBegin and the corresponding execution of fglEnd.
ASSOCIATED GETS
fglGet with argument GL_FOG_FUNC_SGIS
fglGet with argument GL_FOG_FUNC_POINTS_SGIS
fglGet with argument GL_MAX_FOG_FUNC_POINTS_SGIS
MACHINE DEPENDENCIES
Fog mode GL_FOG_FUNC_SGIS is supported only on InfiniteReality systems.
SEE ALSO
fglFog
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