GLAPI/glTexParameter

glTexParameter

Core in version		4.6
Core since version		1.0

glTexParameter: set texture parameters

Function Definition

 void glTexParameterf(GLenum target​, GLenum pname​, GLfloat param​);
 void glTexParameteri(GLenum target​, GLenum pname​, GLint param​);

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​.

Function Definition

 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​);

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 and the stencil component will be discarded. If the depth stencil mode is GL_STENCIL_COMPONENT then the stencil component is returned in 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_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 substituted with 0.0. If GL_TEXTURE_SWIZZLE_R is GL_ONE, the value for r will be substituted 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_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 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 2ⁿ × 2^m, there are max(n, m) + 1 mipmaps. The first mipmap is the original texture, with dimensions 2ⁿ × 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 or l. 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. 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_BORDER, GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT, GL_MIRROR_CLAMP_TO_EDGE, or GL_REPEAT. GL_CLAMP_TO_BORDER causes the s coordinate to be clamped to the range $\left[{\tfrac {-1}{2N}},1+{\tfrac {1}{2N}}\right]$, 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 $\left[{\tfrac {1}{2N}},1-{\tfrac {1}{2N}}\right]$, 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 s coordinate to be clamped as follows: $min(1-{\tfrac {1}{2*N}},max({\tfrac {1}{2*N}},abs(coord)))$. 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_BORDER, GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT, GL_MIRROR_CLAMP_TO_EDGE, 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_BORDER, GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT, GL_MIRROR_CLAMP_TO_EDGE, 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).

If the I form of glTexParameter or glSamplerParameter are used, and GL_TEXTURE_BORDER_COLOR is specified, then the data are stored as signed or unsigned integer values, as is the appropriate type. When not using the I forms, the values are converted to floating-point.

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 Comparison Function	Computed result
GL_LEQUAL	$result={\begin{cases}1.0,&r\leq D_{t}\\0.0,&r>D_{t}\end{cases}}$
GL_GEQUAL	$result={\begin{cases}1.0,&r\geq D_{t}\\0.0,&r<D_{t}\end{cases}}$
GL_LESS	$result={\begin{cases}1.0,&r<D_{t}\\0.0,&r\geq D_{t}\end{cases}}$
GL_GREATER	$result={\begin{cases}1.0,&r>D_{t}\\0.0,&r\leq D_{t}\end{cases}}$
GL_EQUAL	$result={\begin{cases}1.0,&r=D_{t}\\0.0,&r\neq D_{t}\end{cases}}$
GL_NOTEQUAL	$result={\begin{cases}1.0,&r\neq D_{t}\\0.0,&r=D_{t}\end{cases}}$
GL_ALWAYS	$result=1.0$
GL_NEVER	$result=0.0$

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

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, glSamplerParameter

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 LicenseRef-FreeB.