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<STRONG>NAME</STRONG>
<STRONG>glTexEnvf,</STRONG> <STRONG>glTexEnvi,</STRONG> <STRONG>glTexEnvfv,</STRONG> <STRONG>glTexEnviv</STRONG> - set texture
environment parameters
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glTexEnvf</STRONG>( GLenum <EM>target</EM>,
GLenum <EM>pname</EM>,
GLfloat <EM>param</EM> )
void <STRONG>glTexEnvi</STRONG>( GLenum <EM>target</EM>,
GLenum <EM>pname</EM>,
GLint <EM>param</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>target</EM> Specifies a texture environment. Must be
<STRONG>GL_TEXTURE_ENV</STRONG>.
<EM>pname</EM> Specifies the symbolic name of a single-valued
texture environment parameter. Must be
<STRONG>GL_TEXTURE_ENV_MODE</STRONG>.
<EM>param</EM> Specifies a single symbolic constant, one of
<STRONG>GL_MODULATE</STRONG>, <STRONG>GL_DECAL</STRONG>, <STRONG>GL_BLEND</STRONG>, or <STRONG>GL_REPLACE</STRONG>.
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glTexEnvfv</STRONG>( GLenum <EM>target</EM>,
GLenum <EM>pname</EM>,
const GLfloat *<EM>params</EM> )
void <STRONG>glTexEnviv</STRONG>( GLenum <EM>target</EM>,
GLenum <EM>pname</EM>,
const GLint *<EM>params</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>target</EM>
Specifies a texture environment. Must be
<STRONG>GL_TEXTURE_ENV</STRONG>.
<EM>pname</EM>
Specifies the symbolic name of a texture environment
parameter. Accepted values are <STRONG>GL_TEXTURE_ENV_MODE</STRONG> and
<STRONG>GL_TEXTURE_ENV_COLOR</STRONG>.
<EM>params</EM>
Specifies a pointer to a parameter array that contains
either a single symbolic constant or an RGBA color.
<STRONG>DESCRIPTION</STRONG>
A texture environment specifies how texture values are
interpreted when a fragment is textured. <EM>target</EM> must be
<STRONG>GL_TEXTURE_ENV</STRONG>. <EM>pname</EM> can be either <STRONG>GL_TEXTURE_ENV_MODE</STRONG> or
<STRONG>GL_TEXTURE_ENV_COLOR</STRONG>.
If <EM>pname</EM> is <STRONG>GL_TEXTURE_ENV_MODE</STRONG>, then <EM>params</EM> is (or points
to) the symbolic name of a texture function. Four texture
functions may be specified: <STRONG>GL_MODULATE</STRONG>, <STRONG>GL_DECAL</STRONG>,
<STRONG>GL_BLEND</STRONG>, and <STRONG>GL_REPLACE</STRONG>.
A texture function acts on the fragment to be textured using
the texture image value that applies to the fragment (see
<STRONG>glTexParameter</STRONG>) and produces an RGBA color for that
fragment. The following table shows how the RGBA color is
produced for each of the three texture functions that can be
chosen. C is a triple of color values (RGB) and A is the
associated alpha value. RGBA values extracted from a
texture image are in the range [0,1]. The subscript f
refers to the incoming fragment, the subscript t to the
texture image, the subscript c to the texture environment
color, and subscript v indicates a value produced by the
texture function.
A texture image can have up to four components per texture
element (see <STRONG>glTexImage1D</STRONG>, <STRONG>glTexImage2D</STRONG>, <STRONG>glCopyTexImage1D</STRONG>,
and <STRONG>glCopyTexImage2D</STRONG>). In a one-component image, L
indicates that single component. A two-component <STRONG>i</STRONG>mage uses
L and A . A three-component image has only a color value,
Ct. A f<STRONG>o</STRONG>ur-component image has both a color value C and an
a<STRONG>l</STRONG>pha value A . t
t
_______________________________________________________________________
|<EM>Base</EM> <EM>internal</EM> || <EM>Texture</EM> <EM>functions</EM> |
| <EM>format</EM> ||<STRONG>GL_MODULATE</STRONG> <STRONG>GL_DECAL</STRONG> <STRONG>GL_BLEND</STRONG> <STRONG>GL_REPLACE</STRONG> |
<EM>|</EM>______________<EM>||</EM>______________________________________________________|
| <STRONG>GL_ALPHA</STRONG> || C =C | | C =C | C =C |
| || A <STRONG>=</STRONG>A <STRONG>A</STRONG> | undefined | Av=Af | Av=Af |
<EM>|</EM>______________<EM>||</EM>___<STRONG>_</STRONG>__<STRONG>_</STRONG>_<STRONG>_</STRONG>___<EM>|</EM>_____________<EM>|</EM>_____<STRONG>_</STRONG>__<STRONG>_</STRONG>_____<EM>|</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____|
|<STRONG>GL_LUMINANCE</STRONG> || C =L C | undefined | C =(1-L )C | C =L |
| 1 || v t f | | v +L Ct f | v t |
| || | | t c | |
| || A =A | | A =A | A =A |
<EM>|</EM>______________<EM>||</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____<EM>|</EM>_____________<EM>|</EM>______<STRONG>_</STRONG>__<STRONG>_</STRONG>____<EM>|</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____|
|<STRONG>GL_LUMINANCE</STRONG> || C =L C | undefined | C =(1-L )C | C =L |
| <STRONG>_ALPHA</STRONG> || v t f | | v +L <STRONG>C</STRONG> f | v t |
| 2 || | | t c | |
| || A =A A | | A =A A | A =A |
<EM>|</EM>______________<EM>||</EM>___<STRONG>_</STRONG>__<STRONG>_</STRONG>_<STRONG>_</STRONG>___<EM>|</EM>_____________<EM>|</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>_<STRONG>_</STRONG>____<EM>|</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____|
|<STRONG>GL_INTENSITY</STRONG> || C =C I | undefined | C =(1-I )C | C =I |
| || v f t | | v +I Ct f | v t |
| || | | t c | |
| || A =A I | | A =(1-I )A | A =I |
| || v f t | | v +I At f | v t |
<EM>|</EM>______________<EM>||</EM>____________<EM>|</EM>_____________<EM>|</EM>______<STRONG>_</STRONG>_<STRONG>_</STRONG>_____<EM>|</EM>____________|
| <STRONG>GL_RGB</STRONG> || C =C C | C =C | C =(1-C C | C =C |
| 3 || v t f | v t | v +C <STRONG>C</STRONG>) f | v t |
| || | | t c | |
| || A =A | A =A | A =A | A =A |
<EM>|</EM>______________<EM>||</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____<EM>|</EM>_____<STRONG>_</STRONG>__<STRONG>_</STRONG>____<EM>|</EM>_____<STRONG>_</STRONG>__<STRONG>_</STRONG>_____<EM>|</EM>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____|
| <STRONG>GL_RGBA</STRONG> || C =C C | C =(1-A )C | C =(1-C C | C =C |
| 4 || v t f | v +A Ct f | v +C <STRONG>C</STRONG>) f | v t |
| || | t t | t c | |
| || A =A A | A =A | A =A A | A =A |
<EM>|</EM>______________<EM>||</EM>___<STRONG>_</STRONG>__<STRONG>_</STRONG>_<STRONG>_</STRONG>___<EM>|</EM<STRONG>|</STRONG>_____<STRONG>_</STRONG>__<STRONG>_</STRONG>____<EM>|</EM<STRONG>|</STRONG>____<STRONG>_</STRONG>__<STRONG>_</STRONG>_<STRONG>_</STRONG>____<EM>|</EM<STRONG>|</STRONG>____<STRONG>_</STRONG>__<STRONG>_</STRONG>____|
If <EM>pname</EM> is <STRONG>GL_TEXTURE_ENV_COLOR</STRONG>, <EM>params</EM> is a pointer to an
array that holds an RGBA color consisting of four values.
Integer color components are interpreted linearly such that
the most positive integer maps to 1.0, and the most negative
integer maps to -1.0. The values are clamped to the range
[0,1] when they are specified. C takes these four values.
c
<STRONG>GL_TEXTURE_ENV_MODE</STRONG> defaults to <STRONG>GL_MODULATE</STRONG> and
<STRONG>GL_TEXTURE_ENV_COLOR</STRONG> defaults to (0, 0, 0, 0).
<STRONG>NOTES</STRONG>
<STRONG>GL_REPLACE</STRONG> may only be used if the GL version is 1.1 or
greater.
Internal formats other than 1, 2, 3, or 4 may only be used
if the GL version is 1.1 or greater.
<STRONG>ERRORS</STRONG>
<STRONG>GL_INVALID_ENUM</STRONG> is generated when <EM>target</EM> or <EM>pname</EM> is not one
of the accepted defined values, or when <EM>params</EM> should have a
defined constant value (based on the value of <EM>pname</EM>) and
does not.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glTexEnv</STRONG> is executed
between the execution of <STRONG>glBegin</STRONG> and the corresponding
execution of <STRONG>glEnd</STRONG>.
<STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG>
<STRONG>glGetTexEnv</STRONG>
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glCopyPixels</STRONG>, <STRONG>glCopyTexImage1D</STRONG>, <STRONG>glCopyTexImage2D</STRONG>,
<STRONG>glCopyTexSubImage1D</STRONG>, <STRONG>glCopyTexSubImage2D</STRONG>, <STRONG>glTexImage1D</STRONG>,
<STRONG>glTexImage2D</STRONG>, <STRONG>glTexParameter</STRONG>, <STRONG>glTexSubImage1D</STRONG>,
<STRONG>glTexSubImage2D</STRONG>
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