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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_DEPTH_STENCIL_TEXTURE_MODE, 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_DEPTH_STENCIL_TEXTURE_MODE, 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_DEPTH_STENCIL_TEXTURE_MODE
Specifies the mode used to read from depth-stencil format textures. params must be
one of GL_DEPTH_COMPONENT or GL_STENCIL_COMPONENT. If the depth stencil mode is
GL_DEPTH_COMPONENT, then reads from depth-stencil format textures will return the
depth component of the texel in Rt and the stencil component will be discarded. If the
depth stencil mode is GL_STENCIL_COMPONENT then the stencil component is returned in
Rt and the depth component is discarded. The initial value is GL_DEPTH_COMPONENT.
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 × 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 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, GL_REPEAT, or GL_MIRROR_CLAMP_TO_EDGE.
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.
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_CLAMP_TO_BORDER, 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_CLAMP_TO_BORDER, 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.
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().
GL_DEPTH_STENCIL_TEXTURE_MODE is available only if the GL version is 4.3 or greater.
GL_MIRROR_CLAMP_TO_EDGE is available only if the GL version is 4.4 or greater.
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 © 1991-2006 Silicon Graphics, Inc. Copyright © 2012-2013 Khronos Group. This
document is licensed under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
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