glFogfv function
The glFogfv function specifies fog parameters.
void WINAPI glFogfv(
GLenum pname,
const GLfloat *params
);
-
pname
-
Specifies a fog parameter.
Accepts one of the following values.
Value Meaning - GL_FOG_MODE
The params parameter is a 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 in the following Remarks section. The default fog mode is GL_EXP. - GL_FOG_DENSITY
The params parameter is a floating-point value that specifies density, the fog density used in both exponential fog equations. Only nonnegative densities are accepted. The default fog density is 1.0. - GL_FOG_START
The params parameter is a floating-point value that specifies start, the near distance used in the linear fog equation. The default near distance is 0.0. - GL_FOG_END
The params parameter is a floating-point value that specifies end, the far distance used in the linear fog equation. The default far distance is 1.0. - GL_FOG_INDEX
The params parameter is a floating-point value that specifies if , the fog color index. The default fog index is 0.0. - GL_FOG_COLOR
The params parameter contains four floating-point values that specify Cf , 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 default fog color is (0,0,0,0). -
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.
This function does not return a value.
The following error codes can be retrieved by the glGetError function.
Name | Meaning |
---|---|
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pname was not an accepted value. |
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The function was called between a call to glBegin and the corresponding call to glEnd. |
You enable and disable fog with glEnable and glDisable, using the argument GL_FOG. While enabled, fog affects rasterized geometry, bitmaps, and pixel blocks, but not buffer-clear operations.
The glFogfv function assigns the value or values in params to the fog parameter specified by pname.
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:
The equation for GL_EXP fog is:
The equation for GL_EXP2 fog is:
Regardless of the fog mode, f is clamped to the range [0,1] after it is computed. Then, if OpenGL is in RGBA color mode, the fragment's color Cr is replaced by
In color-index mode, the fragment's color index ir is replaced by
The following functions retrieve information related to the glFog functions:
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
glIsEnabled with argument GL_FOG
Requirement | Value |
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Minimum supported client |
Windows 2000 Professional [desktop apps only] |
Minimum supported server |
Windows 2000 Server [desktop apps only] |
Header |
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Library |
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DLL |
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