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GLTEXPARAMETER(3G) OpenGL 3.3 GLTEXPARAMETER(3G)
NAME
glTexParameter - set texture parameters
C SPECIFICATION
void glTexParameterf(GLenum target, GLenum pname, GLfloat param);
void glTexParameteri(GLenum target, GLenum pname, GLint param);
PARAMETERS
target
Specifies the target texture, which must be either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY, GL_TEXTURE_RECTANGLE, or GL_TEXTURE_CUBE_MAP.
pname
Specifies the symbolic name of a single-valued texture parameter. pname can be one of the
following: GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_COMPARE_FUNC, GL_TEXTURE_COMPARE_MODE,
GL_TEXTURE_LOD_BIAS, GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER, GL_TEXTURE_MIN_LOD,
GL_TEXTURE_MAX_LOD, GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_SWIZZLE_R, GL_TEXTURE_SWIZZLE_G,
GL_TEXTURE_SWIZZLE_B, GL_TEXTURE_SWIZZLE_A, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, or
GL_TEXTURE_WRAP_R.
param
Specifies the value of pname.
C SPECIFICATION
void glTexParameterfv(GLenum target, GLenum pname, const GLfloat * params);
void glTexParameteriv(GLenum target, GLenum pname, const GLint * params);
void glTexParameterIiv(GLenum target, GLenum pname, const GLint * params);
void glTexParameterIuiv(GLenum target, GLenum pname, const GLuint * params);
PARAMETERS
target
Specifies the target texture, which must be either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY, GL_TEXTURE_RECTANGLE, or GL_TEXTURE_CUBE_MAP.
pname
Specifies the symbolic name of a texture parameter. pname can be one of the following:
GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_BORDER_COLOR, GL_TEXTURE_COMPARE_FUNC, GL_TEXTURE_COMPARE_MODE,
GL_TEXTURE_LOD_BIAS, GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER, GL_TEXTURE_MIN_LOD,
GL_TEXTURE_MAX_LOD, GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_SWIZZLE_R, GL_TEXTURE_SWIZZLE_G,
GL_TEXTURE_SWIZZLE_B, GL_TEXTURE_SWIZZLE_A, GL_TEXTURE_SWIZZLE_RGBA, GL_TEXTURE_WRAP_S,
GL_TEXTURE_WRAP_T, or GL_TEXTURE_WRAP_R.
params
Specifies a pointer to an array where the value or values of pname are stored.
DESCRIPTION
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, GL_TEXTURE_1D_ARRAY,
GL_TEXTURE_2D_ARRAY, GL_TEXTURE_RECTANGLE, or GL_TEXTURE_3D. The following symbols are accepted in
pname:
GL_TEXTURE_BASE_LEVEL
Specifies the index of the lowest defined mipmap level. This is an integer value. The initial
value is 0.
GL_TEXTURE_BORDER_COLOR
The data in params specifies four values that define the border values that should be used for
border texels. If a texel is sampled from the border of the texture, the values of
GL_TEXTURE_BORDER_COLOR are interpreted as an RGBA color to match the texture's internal format
and substituted for the non-existent texel data. If the texture contains depth components, the
first component of GL_TEXTURE_BORDER_COLOR is interpreted as a depth value. The initial value is
0.0, 0.0, 0.0, 0.0.
If the values for GL_TEXTURE_BORDER_COLOR are specified with glTexParameterIiv or
glTexParameterIuiv, the values are stored unmodified with an internal data type of integer. If
specified with glTexParameteriv, they are converted to floating point with the following
equation: f = 2 c + 1 2 b - 1. If specified with glTexParameterfv, they are stored unmodified as
floating-point values.
GL_TEXTURE_COMPARE_FUNC
Specifies the comparison operator used when GL_TEXTURE_COMPARE_MODE is set to
GL_COMPARE_REF_TO_TEXTURE. Permissible values are:
+------------------------------------------------+-------------------------------------------------------------------------------+
| | |
| Texture | Computed |
|Comparison Function | result |
| | |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_LEQUAL | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | <= |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | > |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_GEQUAL | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | >= |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | < |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_LESS | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | < |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | >= |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_GREATER | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | > |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | <= |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_EQUAL | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | = |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | ^ |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_NOTEQUAL | <div> |
| | |
| | |
| | result |
| | = |
| | |
| | |
| | |
| | |
| | 1.0 |
| | |
| | |
| | 0.0 |
| | |
| | |
| | ^/ |
| | |
| | |
| | |
| | r |
| | ^ |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | r |
| | = |
| | |
| | D |
| | t |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_ALWAYS | <div> |
| | |
| | result |
| | = |
| | 1.0 |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
|GL_NEVER | <div> |
| | |
| | result |
| | = |
| | 0.0 |
| | |
| | </div> |
+------------------------------------------------+-------------------------------------------------------------------------------+
where r is the current interpolated texture coordinate, and D t is the depth texture value
sampled from the currently bound depth texture. result is assigned to the the red channel.
GL_TEXTURE_COMPARE_MODE
Specifies the texture comparison mode for currently bound depth textures. That is, a texture
whose internal format is GL_DEPTH_COMPONENT_*; see glTexImage2D()) Permissible values are:
GL_COMPARE_REF_TO_TEXTURE
Specifies that the interpolated and clamped r texture coordinate should be compared to the
value in the currently bound depth texture. See the discussion of GL_TEXTURE_COMPARE_FUNC for
details of how the comparison is evaluated. The result of the comparison is assigned to the
red channel.
GL_NONE
Specifies that the red channel should be assigned the appropriate value from the currently
bound depth texture.
GL_TEXTURE_LOD_BIAS
params specifies a fixed bias value that is to be added to the level-of-detail parameter for the
texture before texture sampling. The specified value is added to the shader-supplied bias value
(if any) and subsequently clamped into the implementation-defined range - bias max bias max,
where bias max is the value of the implementation defined constant GL_MAX_TEXTURE_LOD_BIAS. The
initial value is 0.0.
GL_TEXTURE_MIN_FILTER
The texture minifying function is used whenever the level-of-detail function used when sampling
from the texture determines that the texture should be minified. There are six defined minifying
functions. Two of them use either the nearest texture elements or a weighted average of multiple
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 max ^, 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:
GL_NEAREST
Returns the value of the texture element that is nearest (in Manhattan distance) to the
specified texture coordinates.
GL_LINEAR
Returns the weighted average of the four texture elements that are closest to the specified
texture coordinates. These can include items wrapped or repeated from other parts of a
texture, depending on the values of GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, and on the exact
mapping.
GL_NEAREST_MIPMAP_NEAREST
Chooses the mipmap that most closely matches the size of the pixel being textured and uses
the GL_NEAREST criterion (the texture element closest to the specified texture coordinates)
to produce a texture value.
GL_LINEAR_MIPMAP_NEAREST
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 specified texture coordinates) to produce a texture value.
GL_NEAREST_MIPMAP_LINEAR
Chooses the two mipmaps that most closely match the size of the pixel being textured and uses
the GL_NEAREST criterion (the texture element closest to the specified texture coordinates )
to produce a texture value from each mipmap. The final texture value is a weighted average of
those two values.
GL_LINEAR_MIPMAP_LINEAR
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 texture elements that are closest to the
specified texture coordinates) 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 multiple 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.
GL_TEXTURE_MAG_FILTER
The texture magnification function is used whenever the level-of-detail function used when
sampling from the texture determines that the texture should be magified. 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.
GL_NEAREST
Returns the value of the texture element that is nearest (in Manhattan distance) to the
specified texture coordinates.
GL_LINEAR
Returns the weighted average of the texture elements that are closest to the specified
texture coordinates. These can include items wrapped or repeated from other parts of a
texture, depending on the values of GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, and on the exact
mapping.
GL_TEXTURE_MIN_LOD
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.
GL_TEXTURE_MAX_LOD
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.
GL_TEXTURE_MAX_LEVEL
Sets the index of the highest defined mipmap level. This is an integer value. The initial value
is 1000.
GL_TEXTURE_SWIZZLE_R
Sets the swizzle that will be applied to the r component of a texel before it is returned to the
shader. Valid values for param are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_ZERO and GL_ONE. If
GL_TEXTURE_SWIZZLE_R is GL_RED, the value for r will be taken from the first channel of the
fetched texel. If GL_TEXTURE_SWIZZLE_R is GL_GREEN, the value for r will be taken from the second
channel of the fetched texel. If GL_TEXTURE_SWIZZLE_R is GL_BLUE, the value for r will be taken
from the third channel of the fetched texel. If GL_TEXTURE_SWIZZLE_R is GL_ALPHA, the value for r
will be taken from the fourth channel of the fetched texel. If GL_TEXTURE_SWIZZLE_R is GL_ZERO,
the value for r will be subtituted with 0.0. If GL_TEXTURE_SWIZZLE_R is GL_ONE, the value for r
will be subtituted with 1.0. The initial value is GL_RED.
GL_TEXTURE_SWIZZLE_G
Sets the swizzle that will be applied to the g component of a texel before it is returned to the
shader. Valid values for param and their effects are similar to those of GL_TEXTURE_SWIZZLE_R.
The initial value is GL_GREEN.
GL_TEXTURE_SWIZZLE_B
Sets the swizzle that will be applied to the b component of a texel before it is returned to the
shader. Valid values for param and their effects are similar to those of GL_TEXTURE_SWIZZLE_R.
The initial value is GL_BLUE.
GL_TEXTURE_SWIZZLE_A
Sets the swizzle that will be applied to the a component of a texel before it is returned to the
shader. Valid values for param and their effects are similar to those of GL_TEXTURE_SWIZZLE_R.
The initial value is GL_ALPHA.
GL_TEXTURE_SWIZZLE_RGBA
Sets the swizzles that will be applied to the r, g, b, and a components of a texel before they
are returned to the shader. Valid values for params and their effects are similar to those of
GL_TEXTURE_SWIZZLE_R, except that all channels are specified simultaneously. Setting the value of
GL_TEXTURE_SWIZZLE_RGBA is equivalent (assuming no errors are generated) to setting the
parameters of each of GL_TEXTURE_SWIZZLE_R, GL_TEXTURE_SWIZZLE_G, GL_TEXTURE_SWIZZLE_B, and
GL_TEXTURE_SWIZZLE_A successively.
GL_TEXTURE_WRAP_S
Sets the wrap parameter for texture coordinate s to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. GL_CLAMP_TO_EDGE causes s coordinates to be clamped to the
range 1 2N 1 - 1 2N, where N is the size of the texture in the direction of clamping.
GL_CLAMP_TO_BORDER evaluates s coordinates in a similar manner to GL_CLAMP_TO_EDGE. However, in
cases where clamping would have occurred in GL_CLAMP_TO_EDGE mode, the fetched texel data is
substituted with the values specified by GL_TEXTURE_BORDER_COLOR. 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. GL_MIRRORED_REPEAT causes the s coordinate to be set to the fractional part
of the texture coordinate if the integer part of s is even; if the integer part of s is odd, then
the s texture coordinate is set to 1 - frac ^, s, where frac ^, s represents the fractional part
of s. Initially, GL_TEXTURE_WRAP_S is set to GL_REPEAT.
GL_TEXTURE_WRAP_T
Sets the wrap parameter for texture coordinate t to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. See the discussion under GL_TEXTURE_WRAP_S. Initially,
GL_TEXTURE_WRAP_T is set to GL_REPEAT.
GL_TEXTURE_WRAP_R
Sets the wrap parameter for texture coordinate r to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. See the discussion under GL_TEXTURE_WRAP_S. Initially,
GL_TEXTURE_WRAP_R is set to GL_REPEAT.
NOTES
Suppose that a program attempts to sample from a texture 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 the texture is considered incomplete.
Linear filtering accesses the four nearest texture elements only in 2D textures. In 1D textures,
linear filtering accesses the two nearest texture elements. In 3D textures, linear filtering accesses
the eight nearest texture elements.
glTexParameter specifies the texture parameters for the active texture unit, specified by calling
glActiveTexture().
ERRORS
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.
ASSOCIATED GETS
glGetTexParameter()
glGetTexLevelParameter()
SEE ALSO
glActiveTexture(), glBindTexture(), glCopyTexImage1D(), glCopyTexImage2D(), glCopyTexSubImage1D(),
glCopyTexSubImage2D(), glCopyTexSubImage3D(), glPixelStore(), glSamplerParameter(), glTexImage1D(),
glTexImage2D(), glTexImage3D(), glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D()
COPYRIGHT
Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software
B License. For details, see http://oss.sgi.com/projects/FreeB/.
OpenGL 3.3 03/08/2011 GLTEXPARAMETER(3G)
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