glTexParameter

glTexParameterf, glTexParameteri, glTexParameterfv, glTexParameteriv: set texture parameters.

C Specification

void glTexParameterf(
    GLenum	  target,
    GLenum	  pname,
    GLfloat	  param)
void glTexParameteri(
    GLenum	  target,
    GLenum	  pname,
    GLint	  param)
void glTexParameterfv(
    GLenum	  target,
    GLenum	  pname,
    const GLfloat *params) 
void glTexParameteriv(
    GLenum	  target,
    GLenum	  pname,
    const GLint   *params)

Parameters

For scalar versions (see `param`):

target: Specifies the target texture, which must be either GL_TEXTURE_1D, GL_TEXTURE_2D or GL_TEXTURE_3D_EXT.
pname: Specifies the symbolic name of a single-valued texture parameter. pname can be one of the following: GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_PRIORITY, GL_TEXTURE_COMPARE_EXT, or GL_TEXTURE_COMPARE_OPERATOR_EXT.
param: Specifies the value of pname.

For vector versions (see `params`):

target: Specifies the target texture, which must be either GL_TEXTURE_1D or GL_TEXTURE_2D.
pname: Specifies the symbolic name of a texture parameter. pname can be one of the following: GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_BORDER_COLOR, or GL_TEXTURE_PRIORITY.
params: Specifies a pointer to an array where the value or values of pname are stored.

Texture mapping is a technique that applies an image onto an object's surface as if the image were a decal or cellophane shrink-wrap. The image is created in texture space, with an (s, t) coordinate system. A texture is a one- or two-dimensional image and a set of parameters that determine how samples are derived from the image.

glTexParameter assigns the value or values in params to the texture parameter specified as pname. target defines the target texture, either GL_TEXTURE_1D or GL_TEXTURE_2D. 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: 2^a for 1D mipmaps, 2^a2^b for 2D mipmaps, and 2^a2^b2^c for 3D mipmaps.

For example, if a 2D texture has dimensions 2^m2ⁿ, there are max(m, n) + 1 mipmaps. The first mipmap is the original texture, with dimensions 2^m2ⁿ. Each subsequent mipmap has dimensions 2^k-12^l-1, where 2^k2^l are the dimensions of the previous mipmap, until either k=0 or l=0. At that point, subsequent mipmaps have dimension 12^l-1 or 2^k-11 until the final mipmap, which has dimension 11. To define the mipmaps, call glTexImage1D, glTexImage2D, glCopyTexImage1D, glCopyTexImage2D, or glCopyTexImage3DEXT with the level argument indicating the order of the mipmaps. Level 0 is the original texture; level max(m, n ) is the final 11 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_WRAP_S

Sets the wrap parameter for texture coordinate s to GL_CLAMP, GL_REPEAT, GL_CLAMP_TO_BORDER_EXT, or GL_CLAMP_TO_EDGE_EXT. GL_CLAMP causes s coordinates to be clamped to the range [0, 1] and is useful for preventing wrapping artifacts when mapping a single image onto an object. 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_CLAMP_TO_BORDER_EXT causes s coordinates to be clamped to a range 1/2 texel outside [0, 1]; this prevents the "half border, half edge" color artifact. GL_CLAMP_TO_EDGE_EXT causes s coordinates to be clamped to a range 1/2 texel inside [0, 1]; this prevents any border colors from showing up in the image. Border texture elements are accessed only if wrapping is set to GL_CLAMP or GL_CLAMP_TO_BORDER_EXT. Initially, GL_TEXTURE_WRAP_S is set to GL_REPEAT.

GL_TEXTURE_WRAP_T

Sets the wrap parameter for texture coordinate t to GL_CLAMP, GL_REPEAT, GL_CLAMP_TO_BORDER_EXT, or GL_CLAMP_TO_EDGE_EXT. See the discussion under GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_T is set to GL_REPEAT.

GL_TEXTURE_WRAP_R_EXT

Sets the wrap parameter for texture coordinate r to GL_CLAMP, GL_REPEAT, GL_CLAMP_TO_BORDER_EXT, or GL_CLAMP_TO_EDGE_EXT. See the discussion under GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_R_EXT is set to GL_REPEAT.

GL_TEXTURE_BORDER_COLOR

Sets a border color. params contains four values that comprise the RGBA color of the texture border. Integer color components are interpreted linearly such that the most positive integer maps to 1.0, and the most negative integer maps to

1.0. The values are clamped to the range [0, 1] when they are specified. Initially, the border color is (0, 0, 0, 0).

GL_TEXTURE_PRIORITY

Specifies the texture residence priority of the currently bound texture. Permissible values are in the range [0, 1]. See glPrioritizeTextures and glBindTexture for more information.

GL_GENERATE_MIPMAP_EXT

Specifies whether MIP levels should be automatically filtered when the base level (level 0) of a texture map is modified with glTexImage1D, glTexImage2D, glTexImage3DEXT, glTexSubImage1D. glTexSubImage2D, glTexSubImage3DEXT, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, or glCopyTexSubImage3DEXT. The default is GL_FALSE (no automatic generation of MIP levels).

GL_TEXTURE_COMPARE_EXT

Specifies whether the depth texture comparision operator is in effect. param is either GL_TRUE or GL_FALSE. The default is GL_FALSE, meaning that the depth texture comparison operator is not in effect (see GL_TEXTURE_COMPARE_OPERATOR_EXT, below).

GL_TEXTURE_COMPARE_OPERATOR_EXT

Specifies the comparision operator to be used when the depth texture comparison operator is in effect and the texture format is one of the GL_DEPTH formats. param is one of GL_TEXTURE_LEQUAL_R_EXT or GL_TEXTURE_GEQUAL_R_EXT. When the depth texture comparision operator is enabled, the r coordinate is interpolated over the primitive and compared with the depth value found at the interpolated s and t coordinate location in the texture map. This comparison is either less-than-or-equal-to (GL_TEXTURE_LEQUAL_R_EXT) or greater-than-or-equal-to (GL_TEXTURE_GEQUAL_R_EXT). The result of the comparison is 0.0 if it fails, or 1.0 if it passes. If texture filtering is enabled, this comparison is performed for all of the texels involved in the filtering operation, and the resulting values interpolated (note that only GL_LINEAR and GL_NEAREST minification and magnification filters are supported for depth texture comparision). This result is passed down as the alpha component of the texture color to subsequent texture application; the red, green, and blue components are set to 0.0. The depth comparison operator is typically used to produce shadow effects.

Notes

Suppose that a program has enabled texturing (by calling glEnable with argument GL_TEXTURE_1D or GL_TEXTURE_2D) 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, 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 it is as if texture mapping were disabled.

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.

The GL_CLAMP_TO_BORDER_EXT param to GL_WRAP_S, GL_WRAP_T, and GL_WRAP_R_EXT is only supported if the extension GL_EXT_texture_border_clamp is supported.

The GL_CLAMP_TO_EDGE_EXT param to GL_WRAP_S, GL_WRAP_T, and GL_WRAP_R_EXT is only supported if the extension GL_EXT_texture_edge_clamp is supported.

GL_TEXTURE_WRAP_R_EXT and the target GL_TEXTURE_3D_EXT are only supported if the extension GL_EXT_texture3D is supported.

GL_GENERATE_MIPMAP_EXTis only supported if the extension GL_EXT_generate_mipmap is supported.

GL_TEXTURE_COMPARE_EXT and GL_TEXTURE_COMPARE_OPERATOR_EXT are only supported if the extension GL_EXT_shadow is supported.

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.
GL_INVALID_OPERATION is generated if glTexParameter is executed between the execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGetTexParameter
glGetTexLevelParameter

For scalar versions (see param):

For vector versions (see params):

For scalar versions (see `param`):

For vector versions (see `params`):