glTexParameter

NAME

C SPECIFICATION

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

PARAMETERS

C SPECIFICATION

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

PARAMETERS

DESCRIPTION

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.

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 GL_TEXTURE_WRAP_T, and GL_TEXTURE_WRAP_R_EXT, 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.

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 GL_TEXTURE_WRAP_T, and GL_TEXTURE_WRAP_R_EXT, and on the exact mapping.

GL_TEXTURE_MIN_LOD_EXT

Specifies the minimum level-of-detail (LOD) that is allowed. The minimum LOD is set to the value specified by params. Unlike the GL_TEXTURE_MAX_LEVEL_EXT, the minimum LOD can be varied continuously over the full range of the mipmap levels. Setting the minimum LOD allows the application to smoothly manage the transition to a higher- or lower-resolution texture. The default values is -1000.

GL_TEXTURE_MAX_LOD_EXT

Specifies the maximum level-of-detail (LOD) that is allowed. The maximum LOD is set to the value specified by params. Unlike the GL_TEXTURE_MAX_LEVEL_EXT, the maximum LOD can be varied continuously over the full range of the mipmap levels. Setting the maximum LOD allows the application to smoothly manage the transition to a higher- or lower-resolution texture. The default values is 1000.

GL_TEXTURE_BASE_LEVEL_EXT

Specifies the base level of the set of mipmap image arrays. The base level is set to the integer value specified by params. Setting the base level to a value other than 0 permits a subset of mipmaps to be loaded and initially used at a low resolution. Only the levels between base level and max level (inclusive) must be loaded. (Other levels may be loaded, but only the levels from base through max will be used). The default value is 0.

GL_TEXTURE_MAX_LEVEL_EXT

Specifies the maximum level for the set of mipmap image arrays. The maximum level is set to the integer value specified by params. Only the levels between base level and max level (inclusive) must be loaded. (Other levels may be loaded, but only the levels from base through max will be used). The default value is 1000.

GL_TEXTURE_WRAP_S

Sets the wrap parameter for texture coordinate s to either GL_REPEAT, GL_CLAMP, GL_CLAMP_TO_BORDER_EXT, or GL_CLAMP_TO_EDGE_EXT. 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 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_CLAMP_TO_BORDER_EXT causes s coordinates to be clamped to 1/2 texel outside of the map such that the texture filter only samples the border or border color for coordinates outside of the texture map and its border. GL_CLAMP_TO_EDGE_EXT causes s coordinates to be clamped to 1/2 texel within the map such that the texture filter never samples a border texel. 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 either GL_REPEAT, GL_CLAMP, 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 either GL_REPEAT, GL_CLAMP, 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 the automatic generation of mipmap images whenever the base level map is modified. If params is GL_TRUE, the generation of mipmaps is enabled. If params is GL_FALSE, the generation of mipmaps is disabled. Only mipmaps used to "complete" the mipmap array are generated. The method used to generate the mipmap images is implementation-dependent. The GL_GENERATE_MIPMAP_HINT_EXT hint can be used to indicate whether performance or quality is important when generating mipmap images.

NOTES

Linear filtering accesses the four nearest texture elements only in 2D and 3D textures. In 1D textures, linear filtering accesses the two nearest texture elements.

EXTENSIONS

GL_EXT_texture_border_clamp

GL_CLAMP_TO_BORDER_EXT is part of the EXT_texture_border_clamp extension.

GL_EXT_texture_edge_clamp

GL_CLAMP_TO_EDGE_EXT is part of the EXT_texture_edge_clamp extension.

GL_EXT_generate_mipmap

GL_GENERATE_MIPMAP_EXT and GL_GENERATE_MIPMAP_HINT_EXT are part of the EXT_generate_mipmap extension.

GL_EXT_texture_lod

GL_TEXTURE_MIN_LOD_EXT, GL_TEXTURE_MAX_LOD_EXT, GL_TEXTURE_BASE_LEVEL_EXT, and GL_TEXTURE_MAX_LEVEL_EXT are part of the EXT_texture_lod extension.

GL_EXT_texture3D

GL_TEXTURE_3D_EXT and GL_TEXTURE_WRAP_R_EXT are part of the EXT_texture3D extension.

ERRORS

GL_INVALID_ENUM is generated if params should have a defined constant value (based on the value of pname) and does not.

GL_INVALID_VALUE is generated if the GL_TEXTURE_BASE_LEVEL_EXT or GL_TEXTURE_MAX_LEVEL_EXT is negative.

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

ASSOCIATED GETS

SEE ALSO