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GLSAMPLERPARAMETER(3G) OpenGL 3.3 GLSAMPLERPARAMETER(3G)
NAME
glSamplerParameter - set sampler parameters
C SPECIFICATION
void glSamplerParameterf(GLuint sampler, GLenum pname, GLfloat param);
void glSamplerParameteri(GLuint sampler, GLenum pname, GLint param);
PARAMETERS
sampler
Specifies the sampler object whose parameter to modify.
pname
Specifies the symbolic name of a single-valued sampler parameter. pname can be one of the
following: GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_R, GL_TEXTURE_MIN_FILTER,
GL_TEXTURE_MAG_FILTER, GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD, GL_TEXTURE_LOD_BIAS
GL_TEXTURE_COMPARE_MODE, or GL_TEXTURE_COMPARE_FUNC.
param
Specifies the value of pname.
C SPECIFICATION
void glSamplerParameterfv(GLuint sampler, GLenum pname, const GLfloat * params);
void glSamplerParameteriv(GLuint sampler, GLenum pname, const GLint * params);
PARAMETERS
sampler
Specifies the sampler object whose parameter to modify.
pname
Specifies the symbolic name of a sampler parameter. pname can be one of the following:
GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_R, GL_TEXTURE_MIN_FILTER,
GL_TEXTURE_MAG_FILTER, GL_TEXTURE_BORDER_COLOR, GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD,
GL_TEXTURE_LOD_BIAS GL_TEXTURE_COMPARE_MODE, or GL_TEXTURE_COMPARE_FUNC.
params
Specifies a pointer to an array where the value or values of pname are stored.
DESCRIPTION
glSamplerParameter assigns the value or values in params to the sampler parameter specified as pname.
sampler specifies the sampler object to be modified, and must be the name of a sampler object
previously returned from a call to glGenSamplers(). The following symbols are accepted in pname:
GL_TEXTURE_MIN_FILTER
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 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
center of the pixel being textured.
GL_LINEAR
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.
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 nearest to the center of the pixel) 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 center of the pixel) 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 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.
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 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.
GL_TEXTURE_MAG_FILTER
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.
GL_NEAREST
Returns the value of the texture element that is nearest (in Manhattan distance) to the
center of the pixel being textured.
GL_LINEAR
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.
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_WRAP_S
Sets the wrap parameter for texture coordinate s to either GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT,
or GL_REPEAT. GL_CLAMP_TO_BORDER causes the s coordinate 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_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_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 1frac
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_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_MIRRORED_REPEAT,
or GL_REPEAT. See the discussion under GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_R is set to
GL_REPEAT.
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.
GL_TEXTURE_COMPARE_MODE
Specifies the texture comparison mode for currently bound 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 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 texture.
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 texture value sampled from
the currently bound texture. result is assigned to R t.
NOTES
glSamplerParameter is available only if the GL version is 3.3 or higher.
If a sampler object is bound to a texture unit and that unit is used to sample from a texture, the
parameters in the sampler are used to sample from the texture, rather than the equivalent parameters
in the texture object bound to that unit. This introduces the possibility of sampling from the same
texture object with different sets of sampler state, which may lead to a condition where a texture is
incomplete with respect to one sampler object and not with respect to another. Thus, completeness can
be considered a function of a sampler object and a texture object bound to a single texture unit,
rather than a property of the texture object itself.
ERRORS
GL_INVALID_VALUE is generated if sampler is not the name of a sampler object previously returned from
a call to glGenSamplers().
GL_INVALID_ENUM is generated if params should have a defined constant value (based on the value of
pname) and does not.
ASSOCIATED GETS
glGetSamplerParameter()
SEE ALSO
glGenSamplers(), glBindSampler(), glDeleteSamplers(), glIsSampler(), glBindTexture(),
glTexParameter()
COPYRIGHT
Copyright (C) 2010 Khronos Group. This material may be distributed subject to the terms and
conditions set forth in the Open Publication License, v 1.0, 8 June 1999.
http://opencontent.org/openpub/.
OpenGL 3.3 03/08/2011 GLSAMPLERPARAMETER(3G)
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