glTexParameter — set texture parameters
void glTexParameterf (GLenum target,
GLenum pname,
GLfloat param);
void glTexParameteri (GLenum target,
GLenum pname,
GLint param);
Specifies the target texture, which must be either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
or GL_TEXTURE_CUBE_MAP.
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_MIN_LOD, GL_TEXTURE_MAX_LOD,
GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T,
GL_TEXTURE_WRAP_R, GL_TEXTURE_PRIORITY, GL_TEXTURE_COMPARE_MODE,
GL_TEXTURE_COMPARE_FUNC, GL_DEPTH_TEXTURE_MODE, or GL_GENERATE_MIPMAP.
Specifies the value of pname.
void glTexParameterfv (GLenum target,
GLenum pname,
const GLfloat *params);
void glTexParameteriv (GLenum target,
GLenum pname,
const GLint *params);
Specifies the target texture, which must be either GL_TEXTURE_1D, GL_TEXTURE_2D or
GL_TEXTURE_3D.
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_MIN_LOD, GL_TEXTURE_MAX_LOD, GL_TEXTURE_BASE_LEVEL,
GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_WRAP_S, GL_TEXTURE_WRAP_T, GL_TEXTURE_WRAP_R,
GL_TEXTURE_BORDER_COLOR, GL_TEXTURE_PRIORITY, GL_TEXTURE_COMPARE_MODE,
GL_TEXTURE_COMPARE_FUNC, GL_DEPTH_TEXTURE_MODE, or GL_GENERATE_MIPMAP.
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, GL_TEXTURE_2D, or GL_TEXTURE_3D.
The following symbols are accepted in pname:
GL_TEXTURE_MIN_FILTERThe 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×2m, there are max (n, m) + 1 mipmaps. The first mipmap is the original texture, with dimensions 2n×2m. Each subsequent mipmap has dimensions 2k-1×2l-2, where 2k×2l are the dimensions of the previous mipmap, until either k=0 or l=0. At that point, subsequent mipmaps have dimension 1×2l-1 or 2k-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_NEARESTReturns the value of the texture element that is nearest (in Manhattan distance) to the center of the pixel being textured.
GL_LINEARReturns 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_NEARESTChooses 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_NEARESTChooses 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_LINEARChooses 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_LINEARChooses 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_FILTERThe 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_NEARESTReturns the value of the texture element that is nearest (in Manhattan distance) to the center of the pixel being textured.
GL_LINEARReturns 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_LODSets 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_LODSets 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_BASE_LEVELSpecifies the index of the lowest defined mipmap level. This is an integer value. The initial value is 0.
GL_TEXTURE_MAX_LEVELSets the index of the highest defined mipmap level. This is an integer value. The initial value is 1000.
GL_TEXTURE_WRAP_SSets the wrap parameter for texture coordinate s to either GL_CLAMP, GL_CLAMP_TO_BORDER,
GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT, or GL_REPEAT. 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 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. Border texture elements are
accessed only if wrapping is set to GL_CLAMP or GL_CLAMP_TO_BORDER. Initially,
GL_TEXTURE_WRAP_S is set to GL_REPEAT.
GL_TEXTURE_WRAP_TSets the wrap parameter for texture coordinate t to either GL_CLAMP, GL_CLAMP_TO_BORDER,
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_RSets the wrap parameter for texture coordinate r to either GL_CLAMP, GL_CLAMP_TO_BORDER,
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_COLORSets 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_PRIORITYSpecifies 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_TEXTURE_COMPARE_MODESpecifies 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_R_TO_TEXTURESpecifies 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 luminance, intensity, or alpha (as specified by
GL_DEPTH_TEXTURE_MODE).
GL_NONESpecifies that the luminance, intensity, or alpha (as specified by GL_DEPTH_TEXTURE_MODE) should be assigned the
appropriate value from the currently bound depth texture.
GL_TEXTURE_COMPARE_FUNCSpecifies the comparison operator used when GL_TEXTURE_COMPARE_MODE is set to GL_COMPARE_R_TO_TEXTURE.
Permissible values are:
| Texture Comparison Function | Computed result |
|---|---|
GL_LEQUAL | 1.0 if r<=Dt 0.0 if r>Dt |
GL_GEQUAL | 1.0 if r>=Dt 0.0 if r<Dt |
GL_LESS | 1.0 if r<Dt 0.0 if r>=Dt |
GL_GREATER | 1.0 if r>Dt 0.0 if r<=Dt |
GL_EQUAL | 1.0 if r= D t 0.0 if r!=t |
GL_NOTEQUAL | 1.0 if r!=Dt 0.0 if r = Dt |
GL_ALWAYS | 1.0 |
GL_NEVER | 0.0 |
where r is the current interpolated texture coordinate, and Dt is the depth texture value sampled from the
currently bound depth texture. result is assigned to the either the luminance, intensity, or alpha (as specified by
GL_DEPTH_TEXTURE_MODE.)
GL_DEPTH_TEXTURE_MODESpecifies a single symbolic constant indicating how depth values should be treated during filtering and texture application. Accepted
values are GL_LUMINANCE, GL_INTENSITY, and GL_ALPHA. The initial value is
GL_LUMINANCE.
GL_GENERATE_MIPMAPSpecifies a boolean value that indicates if all levels of a mipmap array should be automatically updated when any modification to the
base level mipmap is done. The initial value is GL_FALSE.
GL_TEXTURE_3D, GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD, GL_CLAMP_TO_EDGE,
GL_TEXTURE_BASE_LEVEL, and GL_TEXTURE_MAX_LEVEL are available only if the GL version is 1.2 or greater.
GL_CLAMP_TO_BORDER is available only if the GL version is 1.3 or greater.
GL_MIRRORED_REPEAT, GL_TEXTURE_COMPARE_MODE, GL_TEXTURE_COMPARE_FUNC,
GL_DEPTH_TEXTURE_MODE, and GL_GENERATE_MIPMAP are available only if the GL version is 1.4 or greater.
GL_TEXTURE_COMPARE_FUNC allows the following additional comparison modes only if the GL version is 1.5 or greater:
GL_LESS, GL_GREATER, GL_EQUAL, GL_NOTEQUAL, GL_ALWAYS, and
GL_NEVER.
Suppose that a program has enabled texturing (by calling glEnable with argument GL_TEXTURE_1D,
GL_TEXTURE_2D, or GL_TEXTURE_3D) 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 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.
For OpenGL versions 1.3 and greater, or when the ARB_multitexture extension is supported, glTexParameter specifies the
texture parameters for the active texture unit, specified by calling glActiveTexture.
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.
glActiveTexture, glBindTexture, glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D, glDrawPixels, glPixelStore, glPixelTransfer, glPrioritizeTextures, glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexImage3D, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D