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GLSAMPLERPARAMETER(3G) OpenGL Manual 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);
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_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
× 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, 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 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 © 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
opengl.org 03/16/2013 GLSAMPLERPARAMETER(3G)
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