%mathent; ]> 1991-2006 Silicon Graphics, Inc. 2010-2014 Khronos Group glTexParameter 3G glTexParameter set texture parameters 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 target Specifies the target texture, which must be either GL_TEXTURE_2D, GL_TEXTURE_3D, GL_TEXTURE_2D_ARRAY, or GL_TEXTURE_CUBE_MAP. pname Specifies the symbolic name of a single-valued texture parameter. pname can be one of the following: GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_COMPARE_FUNC, GL_TEXTURE_COMPARE_MODE, 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. params For the vector commands, specifies a pointer to an array where the value or values of pname are stored. glTexParameter assigns the value or values in params to the texture parameter specified as pname. target defines the target texture, either GL_TEXTURE_2D, GL_TEXTURE_CUBE_MAP, GL_TEXTURE_2D_ARRAY, or GL_TEXTURE_3D. The following symbols are accepted in pname: 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_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 = 1.0 0.0 ⁢   r <= D t r > D t GL_GEQUAL result = 1.0 0.0 ⁢   r >= D t r < D t GL_LESS result = 1.0 0.0 ⁢   r < D t r >= D t GL_GREATER result = 1.0 0.0 ⁢   r > D t r <= D t GL_EQUAL result = 1.0 0.0 ⁢   r = D t r ≠ D t GL_NOTEQUAL result = 1.0 0.0 ⁢   r ≠ D t r = D t GL_ALWAYS result = 1.0 GL_NEVER result = 0.0 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_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 glTexImage2D, glTexImage3D, 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. If GL_TEXTURE_SWIZZLE_R is GL_ONE, the value for r will be subtituted with 1 for integer texture components, otherwise 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_WRAP_S Sets the wrap parameter for texture coordinate s to either GL_CLAMP_TO_EDGE, GL_MIRRORED_REPEAT, or GL_REPEAT. 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. 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_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_R Sets the wrap parameter for texture coordinate r to either 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. 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 glTexStorage2D, glTexImage2D, glTexStorage3D, glTexImage3D, 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 texture object bound to 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. glGetTexParameter glTexParameterf glTexParameterfv glTexParameteri glTexParameteriv glActiveTexture, glBindTexture, glCopyTexImage2D, glCopyTexSubImage2D, glCopyTexSubImage3D, glPixelStorei, glSamplerParameter, glTexStorage2D, glTexImage2D, glTexStorage3D, glTexImage3D, glTexSubImage2D, glTexSubImage3D Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2010-2014 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.