glFogf, glFogi, glFogfv, glFogiv - specify fog parameters

glFog
	glFogfv(pname, params[]) -> None
glFogf
	glFogf(pname, param) -> None
glFogfv
	glFogfv(pname, params[]) -> None
glFogi
	glFogi(pname, param) -> None
glFogiv
	glFogiv(pname, params[]) -> None

void glFogf( GLenum pname,
             GLfloat param )
void glFogi( GLenum pname,
             GLint param )

pname	  Specifies a single-valued fog	parameter.
        GL_FOG_MODE, GL_FOG_DENSITY, GL_FOG_START,
        GL_FOG_END, and GL_FOG_INDEX are accepted.

param	  Specifies the	value that pname will be set to.

void glFogfv(	GLenum pname,
              const GLfloat *params )
void glFogiv(	GLenum pname,
              const GLint *params )

pname
     Specifies a fog parameter.  GL_FOG_MODE,
     GL_FOG_DENSITY, GL_FOG_START, GL_FOG_END, GL_FOG_INDEX,
     and GL_FOG_COLOR	are accepted.

params
     Specifies the value or values to	be assigned to pname.
     GL_FOG_COLOR requires an	array of four values.  All
     other parameters	accept an array	containing only	a
     single value.

Fog is initially disabled.  While enabled, fog affects
rasterized geometry, bitmaps,	and pixel blocks, but not
buffer clear operations. To enable and disable fog, call
glEnable and glDisable with argument GL_FOG.

glFog	assigns	the value or values in params to the fog
parameter specified by pname.	 The following values are
accepted for pname:

GL_FOG_MODE	      params is	a single integer or floating-
                    point value that specifies the equation
                    to be used to compute the	fog blend
                    factor, f.  Three	symbolic constants are
                    accepted:	 GL_LINEAR, GL_EXP, and
                    GL_EXP2.	The equations corresponding to
                    these symbolic constants are defined
                    below.  The initial fog mode is GL_EXP.

GL_FOG_DENSITY      params is	a single integer or floating-
                    point value that specifies density, the
                    fog density used in both exponential fog
                    equations.  Only nonnegative densities
                    are accepted.  The initial fog density
                    is 1.

GL_FOG_START	      params is	a single integer or floating-
                    point value that specifies start,	the
                    near distance used in the	linear fog
                    equation.	 The initial near distance is
                    0.

GL_FOG_END	      params is	a single integer or floating-
                    point value that specifies end, the far
                    distance used in the linear fog
                    equation.	 The initial far distance is
                    1.

GL_FOG_INDEX	      params is	a single integer or floating-
                    point value that specifies i , the fog
                    color index.  The	initial	fog index is
                    0.

GL_FOG_COLOR	      params contains four integer or
                    floating-point values that specify C ,
                    the fog color.  Integer values are  f
                    mapped linearly such that	the most
                    positive representable value maps	to
                    1.0, and the most	negative representable
                    value maps to -1.0.  Floating-point
                    values are mapped	directly.  After
                    conversion, all color components are
                    clamped to the range [0,1].  The initial
                    fog color	is (0, 0, 0, 0).

Fog blends a fog color with each rasterized pixel fragment's
posttexturing	color using a blending factor f.  Factor f is
computed in one of three ways, depending on the fog mode.
Let z	be the distance	in eye coordinates from	the origin to
the fragment being fogged.  The equation for GL_LINEAR fog
is

                      f = ___________
                          end	- start

The equation for GL_EXP fog is

                  f =	e**(-(density .	z))

The equation for GL_EXP2 fog is

                 f = e**(-(density . z)**2)

Regardless of	the fog	mode, f	is clamped to the range	[0,1]
after	it is computed.	 Then, if the GL is in RGBA color
mode,	the fragment's color C	is replaced by
                            r
                     C ' = fC	+(1-f)C
                      r      r       f
In color index mode, the fragment's color index i  is
replaced by					   r

                      i ' = i	+(1-f)i
                       r     r       f

GL_INVALID_ENUM is generated if pname	is not an accepted
value, or if pname is	GL_FOG_MODE and	params is not an
accepted value.

GL_INVALID_VALUE is generated	if pname is GL_FOG_DENSITY,
and params is	negative.

GL_INVALID_OPERATION is generated if glFog is	executed
between the execution	of glBegin and the corresponding
execution of glEnd.

glIsEnabled with argument GL_FOG
glGet	with argument GL_FOG_COLOR
glGet	with argument GL_FOG_INDEX
glGet	with argument GL_FOG_DENSITY
glGet	with argument GL_FOG_START
glGet	with argument GL_FOG_END
glGet	with argument GL_FOG_MODE

glEnable