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glTexParameter(3G)
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glTexParameter - set texture parameters
void glTexParameterfv( GLenum target, GLenum pname,
const GLfloat *params ) void glTexParameteriv( GLenum
target, GLenum pname, const GLint *params )
Specifies the target texture, which must be either GL_TEXTURE_1D,
GL_TEXTURE_2D or GL_TEXTURE_3D. Specifies the
symbolic name of a texture parameter. pname can be one of
the following: GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD, GL_TEXTURE_BASE_LEVEL,
GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_WRAP_S,
GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_R, GL_TEXTURE_BORDER_COLOR,
or GL_TEXTURE_PRIORITY. Specifies a pointer to
an array where the value or values of pname are stored.
Texture mapping is a technique that applies an image onto
an object's surface as if the image were a decal or cellophane
shrink-wrap. The image is created in texture space,
with an (s, t) coordinate system. A texture is a one- or
two-dimensional image and a set of parameters that determine
how samples are derived from the image.
glTexParameter assigns the value or values in params to
the texture parameter specified as pname. target defines
the target texture, either GL_TEXTURE_1D, GL_TEXTURE_2D,
or GL_TEXTURE_3D. The following symbols are accepted in
pname: The texture minifying function is used whenever the
pixel being textured maps to an area greater than one texture
element. There are six defined minifying functions.
Two of them use the nearest one or nearest four texture
elements to compute the texture value. The other four use
mipmaps.
A mipmap is an ordered set of arrays representing
the same image at progressively lower resolutions.
If the texture has dimensions 2^n x 2^m, there are
( n, m ) + 1 mipmaps. The first mipmap is the original
texture, with dimensions 2^n X 2^m. Each subsequent
mipmap has dimensions 2^k - 1 x 2^l - 1,
where 2^k x 2^l are the dimensions of the previous
mipmap, until either k = 0 or l = 0. At that point,
subsequent mipmaps have dimension 1 x 2^l - 1 or
2^k - 1 x 1 until the final mipmap, which has
dimension 1 x 1. To define the mipmaps, call
glTexImage1D, glTexImage2D, glTexImage3D, glCopyTexImage1D,
or glCopyTexImage2D with the level
argument indicating the order of the mipmaps. Level
0 is the original texture; level max( n, m ) is the
final 1 x 1 mipmap.
params supplies a function for minifying the texture
as one of the following: Returns the value of
the texture element that is nearest (in Manhattan
distance) to the center of the pixel being textured.
Returns the weighted average of the four
texture elements that are closest to the center of
the pixel being textured. These can include border
texture elements, depending on the values of
GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, and on the
exact mapping. Chooses the mipmap that most
closely matches the size of the pixel being textured
and uses the GL_NEAREST criterion (the texture
element nearest to the center of the pixel) to
produce a texture value. Chooses the mipmap that
most closely matches the size of the pixel being
textured and uses the GL_LINEAR criterion (a
weighted average of the four texture elements that
are closest to the center of the pixel) to produce
a texture value. Chooses the two mipmaps that most
closely match the size of the pixel being textured
and uses the GL_NEAREST criterion (the texture element
nearest to the center of the pixel) to produce
a texture value from each mipmap. The final texture
value is a weighted average of those two values.
Chooses the two mipmaps that most closely
match the size of the pixel being textured and uses
the GL_LINEAR criterion (a weighted average of the
four texture elements that are closest to the center
of the pixel) to produce a texture value from
each mipmap. The final texture value is a weighted
average of those two values.
As more texture elements are sampled in the minification
process, fewer aliasing artifacts will be
apparent. While the GL_NEAREST and GL_LINEAR minification
functions can be faster than the other
four, they sample only one or four texture elements
to determine the texture value of the pixel being
rendered and can produce moire patterns or ragged
transitions. The initial value of GL_TEXTURE_MIN_FILTER
is GL_NEAREST_MIPMAP_LINEAR. The
texture magnification function is used when the
pixel being textured maps to an area less than or
equal to one texture element. It sets the texture
magnification function to either GL_NEAREST or
GL_LINEAR (see below). GL_NEAREST is generally
faster than GL_LINEAR, but it can produce textured
images with sharper edges because the transition
between texture elements is not as smooth. The initial
value of GL_TEXTURE_MAG_FILTER is GL_LINEAR.
Returns the value of the texture element that is
nearest (in Manhattan distance) to the center of
the pixel being textured. Returns the weighted
average of the four texture elements that are closest
to the center of the pixel being textured.
These can include border texture elements, depending
on the values of GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T,
and on the exact mapping.
Sets the minimum level-of-detail parameter. This floating-point
value limits the selection of highest resolution
mipmap (lowest mipmap level). The initial value is -1000.
Sets the maximum level-of-detail parameter. This floating-point
value limits the selection of the lowest resolution
mipmap (highest mipmap level). The initial value is
1000.
Specifies the index of the lowest defined mipmap level.
This is an integer value. The initial value is 0.
Sets the index of the highest defined mipmap level. This
is an integer value. The initial value is 1000.
Sets the wrap parameter for texture coordinate s to either
GL_CLAMP, GL_CLAMP_TO_EDGE, or GL_REPEAT. GL_CLAMP causes
s coordinates to be clamped to the range [0,1] and is useful
for preventing wrapping artifacts when mapping a single
image onto an object. GL_CLAMP_TO_EDGE causes s coordinates
to be clamped to the range [ {1 over 2N}, 1 - {1
over 2N} ], where N is the size of the texture in the
direction of clamping. GL_REPEAT causes the integer part
of the s coordinate to be ignored; the GL uses only the
fractional part, thereby creating a repeating pattern.
Border texture elements are accessed only if wrapping is
set to GL_CLAMP. Initially, GL_TEXTURE_WRAP_S is set to
GL_REPEAT.
Sets the wrap parameter for texture coordinate t to either
GL_CLAMP, GL_CLAMP_TO_EDGE, or GL_REPEAT. See the discussion
under GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_T
is set to GL_REPEAT. Sets the wrap parameter for texture
coordinate r to either GL_CLAMP, GL_CLAMP_TO_EDGE, or
GL_REPEAT. See the discussion under GL_TEXTURE_WRAP_S.
Initially, GL_TEXTURE_WRAP_R is set to GL_REPEAT. Sets a
border color. params contains four values that comprise
the RGBA color of the texture border. 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. Initially, the border color is (0, 0, 0,
0). Specifies the texture residence priority of the currently
bound texture. Permissible values are in the range
[0, 1]. See glPrioritizeTextures and glBindTexture for
more information.
GL_TEXTURE_3D, GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD,
GL_TEXTURE_BASE_LEVEL, and GL_TEXTURE_MAX_LEVEL are only
available if the GL version is 1.2 or greater.
Suppose that a program has enabled texturing (by calling
glEnable with argument GL_TEXTURE_1D, GL_TEXTURE_2D, or
GL_TEXTURE_3D) and has set GL_TEXTURE_MIN_FILTER to one of
the functions that requires a mipmap. If either the dimensions
of the texture images currently defined (with previous
calls to glTexImage1D, glTexImage2D, glTexImage3D,
glCopyTexImage1D, or glCopyTexImage2D) do not follow the
proper sequence for mipmaps (described above), or there
are fewer texture images defined than are needed, or the
set of texture images have differing numbers of texture
components, then it is as if texture mapping were disabled.
Linear filtering accesses the four nearest texture elements
only in 2D textures. In 1D textures, linear filtering
accesses the two nearest texture elements.
When the GL_ARB_multitexture extension is supported, glTexParameter
specifies the texture parameters for the
active texture unit, specified by calling glActiveTextureARB.
GL_INVALID_ENUM is generated if target or pname is not one
of the accepted defined values.
GL_INVALID_ENUM is generated if params should have a
defined constant value (based on the value of pname) and
does not.
GL_INVALID_OPERATION is generated if glTexParameter is
executed between the execution of glBegin and the corresponding
execution of glEnd.
void glTexParameterf(
(GLenum target,,
GLfloat param,,
GLenum pname) ); void glTexParameteri(
(GLenum target,,
GLenum pname,,
GLint param) );
Specifies the target texture, which must be either GL_TEXTURE_1D,
GL_TEXTURE_2D, or GL_TEXTURE_3D. Specifies the
symbolic name of a single-valued texture parameter. pname
can be one of the following: GL_TEXTURE_MIN_FILTER,
GL_TEXTURE_MAG_FILTER, GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD,
GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_MAX_LEVEL,
GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_R,
or GL_TEXTURE_PRIORITY. Specifies the value of pname.
glGetTexParameter glGetTexLevelParameter
glActiveTextureARB(3), glBindTexture(3), glCopyPixels(3),
glCopyTexImage1D(3), glCopyTexImage2D(3), glCopyTexSubImage1D(3), glCopyTexSubImage2D(3), glCopyTexSubImage3D(3),
glDrawPixels(3), glPixelStore(3), glPixelTransfer(3),
glPrioritizeTextures(3), glTexEnv(3), glTexGen(3), glTexImage1D(3), glTexImage2D(3), glTexImage3D(3), glTexSubImage1D(3), (3), glTexSubImage2D(3glTexSubImage3D),
glTexParameter(3G)
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