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Alphabetical
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glTexEnv(3G)
NAME
glTexEnv, glTexEnvf, glTexEnvi, glTexEnvfv, glTexEnviv - set texture
environment parameters
SYNOPSIS
void glTexEnvf(
GLenum target,
GLenum pname,
GLfloat param );
void glTexEnvi(
GLenum target,
GLenum pname,
GLint param );
PARAMETERS
target
Specifies a texture environment. Must be GL_TEXTURE_ENV.
pname
Specifies the symbolic name of a single-valued texture environment
parameter. Must be GL_TEXTURE_ENV_MODE.
param
Specifies a single symbolic constant, one of GL_MODULATE, GL_DECAL,
GL_BLEND, or GL_REPLACE.
SYNOPSIS
void glTexEnvfv(
GLenum target,
GLenum pname,
const GLfloat *params );
void glTexEnviv(
GLenum target,
GLenum pname,
const GLint *params );
PARAMETERS
target
Specifies a texture environment. Must be GL_TEXTURE_ENV.
pname
Specifies the symbolic name of a texture environment parameter.
Accepted values are GL_TEXTURE_ENV_MODE and GL_TEXTURE_ENV_COLOR.
params
Specifies a pointer to a parameter array that contains either a single
symbolic constant or an RGBA color.
DESCRIPTION
A texture environment specifies how texture values are interpreted when a
fragment is textured. target must be GL_TEXTURE_ENV. pname can be either
GL_TEXTURE_ENV_MODE or GL_TEXTURE_ENV_COLOR.
If pname is GL_TEXTURE_ENV_MODE, then params is (or points to) the symbolic
name of a texture function. Four texture functions may be specified:
GL_MODULATE, GL_DECAL, GL_BLEND, and GL_REPLACE.
A texture function acts on the fragment to be textured using the texture
image value that applies to the fragment (see glTexParameter()) 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
glTexImage1D(), glTexImage2D(), glTexImage3D(), glCopyTexImage1D(), and
glCopyTexImage2D()). In a one-component image, L[t] indicates that single
component. A two-component image uses L[t] and A[t]. A three-component
image has only a color value, C[t]. A four-component image has both a color
value C[t] and an alpha value A[t].
__________________________________________________________________________________________________________________________________________________________
Texture Functions
Base
internal
format GL_MODULATE GL_DECAL GL_BLEND GL_REPLACE
__________________________________________________________________________________________________________________________________________________________
GL_ALPHA undefined
C[v] = C[f]A[v] = A[f] A[t]
C[v] = C[f]A[v] = A[f]
C[v] = C[f]A[v] = A[t]
undefined
GL_LUMINANCE
(or 1)
C[v] = L[t] C[f]
A[v] = A[f]
C[v] = ( 1 - L[t] ) C[f]
+ L[t] C[c]
A[v] = A[f]
C[v] = L[t]
A[v] = A[f]
undefined
GL_LUMINANCE_ALPHA
(or 2)
C[v] = L[t] C[f]
A[v] = A[t] A[f]
C[v] = ( 1 - L[t] ) C[f]
+ L[t] C[c]
A[v] = A[t] A[f]
C[v] = L[t]
A[v] = A[t]
undefined
GL_INTENSITY
C[v] = C[f] I[t]
A[v] = A[f] I[t]
C[v] = ( 1 - I[t] ) C[f]
+ I[t] C[c]
A[v] = ( 1 - I[t] ) A[f]
+ I[t] A[c]
C[v] = I[t]
A[v] = I[t]
GL_RGB (or
3)
C[v] = C[t] C[f]
A[v] = A[f]
C[v] = C[t]
A[v] = A[f]
C[v] = (1 - C[t]) C[f]
+ C[t] C[c]
A[v] = A[f]
C[v] = C[t]
A[v] = A[f]
GL_RGBA (or
4)
C[v] = C[t] C[f]
A[v] = A[t] A[f]
C[v] = ( 1 - A[t]) C[f]
+ A[t] C[t]
A[v] = A[f]
C[v] = (1 - C[t]) C[f]
+ C[t] C[c]
A[v] = A[t] A[f]
C[v] = C[t]
A[v] = A[t]
__________________________________________________________________________________________________________________________________________________________
If pname is GL_TEXTURE_ENV_COLOR,params 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[c] takes these four values.
GL_TEXTURE_ENV_MODE defaults to GL_MODULATE andGL_TEXTURE_ENV_COLOR
defaults to (0, 0, 0, 0).
NOTES
GL_REPLACE 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.
When the GL_ARB_multitexture extension is supported, glTexEnv() controls
the texture environment for the current active texture unit, selected
byglActiveTextureARB(). GL_INVALID_ENUM is generated when target or pname
is not one of the accepted defined values, or when params should have a
defined constant value (based on the value of pname) and does not.
GL_INVALID_OPERATION is generated if glTexEnv()is executed between the
execution of glBegin()and the corresponding execution of glEnd().
ASSOCIATED GETS
glGetTexEnv()
SEE ALSO
glActiveTextureARB(3), glCopyPixels(3), glCopyTexImage1D(3),
glCopyTexImage2D(3), glCopyTexSubImage1D(3), glCopyTexSubImage2D(3),
glCopyTexSubImage3D(3), glTexImage1D(3), glTexImage2D(3), glTexImage3D(3),
glTexParameter(3), glTexSubImage1D(3), glTexSubImage2D(3),
glTexSubImage3D(3)
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Index for
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Alphabetical
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