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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_BIASGL_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);
void glSamplerParameterIiv(GLuint sampler, GLenum pname, const GLint *params);
void glSamplerParameterIuiv(GLuint sampler, GLenum pname, const GLuint *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_BIASGL_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 × 2 m, there are max n m + 1
mipmaps. The first mipmap is the original texture, with dimensions 2 n × 2 m. Each
subsequent mipmap has dimensions 2 k - 1 × 2 l - 1, where 2 k × 2 l are the dimensions
of the previous mipmap, until either k = 0 or l = 0. At that point, subsequent mipmaps
have dimension 1 × 2 l - 1 or 2 k - 1 × 1 until the final mipmap, which has dimension
1 × 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 × 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, GL_REPEAT, or GL_MIRROR_CLAMP_TO_EDGE. 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 s, where frac s represents the
fractional part of s. GL_MIRROR_CLAMP_TO_EDGE causes the the s coordinate to be
repeated as for GL_MIRRORED_REPEAT for one reptition of the texture, at which point
the coordinate to be clamped as in GL_CLAMP_TO_EDGE. 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, GL_REPEAT, or GL_MIRROR_CLAMP_TO_EDGE. 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, GL_REPEAT, or GL_MIRROR_CLAMP_TO_EDGE. 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.
GL_MIRROR_CLAMP_TO_EDGE is available only if the GL version is 4.4 or greater.
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 © 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/.
AUTHORS
opengl.org