glSamplerParameter — set sampler parameters
void glSamplerParameterf( | GLuint | sampler, |
GLenum | pname, | |
GLfloat | param) ; |
void glSamplerParameteri( | GLuint | sampler, |
GLenum | pname, | |
GLint | param) ; |
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
.
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) ; |
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.
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
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
GL_CLAMP_TO_EDGE
, GL_MIRRORED_REPEAT
, or
GL_REPEAT
. GL_CLAMP_TO_BORDER
causes the
GL_CLAMP_TO_EDGE
causes
GL_REPEAT
causes the
integer part of the
GL_MIRRORED_REPEAT
causes the
GL_TEXTURE_WRAP_S
is set to GL_REPEAT
.
GL_TEXTURE_WRAP_T
Sets the wrap parameter for texture coordinate
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
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
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
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 Comparison Function | Computed result |
---|---|
GL_LEQUAL
|
|
GL_GEQUAL
|
|
GL_LESS
|
|
GL_GREATER
|
|
GL_EQUAL
|
|
GL_NOTEQUAL
|
|
GL_ALWAYS
|
|
GL_NEVER
|
|
where
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_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.
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/.