Table of Contents
glFogf, glFogi, glFogfv, glFogiv - specify fog parameters
void
glFogf( GLenum pname,
GLfloat param )
void glFogi( GLenum pname,
GLint param )
eqn not supported
- 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 $i sub f$, the fog
color index. The initial fog index is 0.
- GL_FOG_COLOR
- params contains four
integer or floating-point values that specify $C sub f$, the fog color. Integer
values are 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
eqn not
supported
The equation for GL_EXP fog is
eqn not supported
The equation
for GL_EXP2 fog is
eqn not supported
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 red, green, and blue colors, represented by $C
sub r$, are replaced by
eqn not supported
Fog does not affect a fragment's
alpha component.
In color index mode, the fragment's color index $i sub r$
is replaced by
eqn not supported
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(3G)
Table of Contents