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GLTEXPARAMETER(3gl)					   GLTEXPARAMETER(3gl)

NAME
       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 )

PARAMETERS
       target  Specifies the target texture, must  be  GL_TEXTURE_1D,  GL_TEX‐
	       TURE_2D,	 GL_TEXTURE_3D,	 GL_TEXTURE_CUBE_MAP or GL_DETAIL_TEX‐
	       TURE_2D_SGIS.

       pname   Specifies the symbolic name of a single-valued texture  parame‐
	       ter.  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_WRAP_R,   GL_TEXTURE_PRIORITY,   GL_TEXTURE_MIN_LOD,
	       GL_TEXTURE_MAX_LOD,	 GL_TEXTURE_BASE_LEVEL,	       GL_TEX‐
	       TURE_MAX_LEVEL,	 GL_TEXTURE_COMPARE_FUNC,  GL_GENERATE_MIPMAP,
	       GL_TEXTURE_LOD_BIAS_S_SGIX,   GL_TEXTURE_LOD_BIAS_T_SGIX,    or
	       GL_TEXTURE_LOD_BIAS_R_SGIX.

       param   Specifies the value of pname.

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

PARAMETERS
       target Specifies	 the  target  texture,	GL_TEXTURE_1D,	GL_TEXTURE_2D,
	      GL_TEXTURE_3D, GL_TEXTURE_CUBE_MAP or GL_DETAIL_TEXTURE_2D_SGIS.

       pname  Specifies the symbolic name of a texture parameter.   pname  can
	      be   one	 of   the  following:  GL_TEXTURE_MIN_FILTER,  GL_TEX‐
	      TURE_MAG_FILTER, GL_TEXTURE_WRAP_S,  GL_TEXTURE_WRAP_T,  GL_TEX‐
	      TURE_WRAP_R, GL_LINEAR_DETAIL_SGIS, GL_LINEAR_DETAIL_ALPHA_SGIS,
	      GL_LINEAR_DETAIL_COLOR_SGIS,  GL_TEXTURE_BORDER_COLOR,   GL_TEX‐
	      TURE_PRIORITY,  GL_TEXTURE_MIN_LOD,  GL_TEXTURE_MAX_LOD, GL_TEX‐
	      TURE_BASE_LEVEL, GL_TEXTURE_MAX_LEVEL,  GL_TEXTURE_COMPARE_FUNC,
	      GL_GENERATE_MIPMAP,      GL_TEXTURE_LOD_BIAS_S_SGIX,     GL_TEX‐
	      TURE_LOD_BIAS_T_SGIX, GL_TEXTURE_LOD_BIAS_R_SGIX.	  GL_POST_TEX‐
	      TURE_FILTER_SCALE_SGIX,	GL_POST_TEXTURE_FILTER_BIAS_SGIX,   or
	      GL_TEXTURE_MAX_ANISOTROPY_EXT.

       params Specifies a pointer to an array where the	 value	or  values  of
	      pname are stored.

DESCRIPTION
       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, r) coordinate system.
       A texture is a one- two- or three-dimensional image and a set of param‐
       eters 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, GL_TEXTURE_3D, GL_TEXTURE_CUBE_MAP
       or GL_DETAIL_TEXTURE_2D_SGIS.  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  ele‐
		 ment.	 There	are  six  defined minifying functions.	Two of
		 them use the nearest one or nearest eight 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×2l	at  GL_TEXTURE_BASE_LEVEL,  there  are
		 max(n,m,l)+1 mipmaps.	The first mipmap is the original  tex‐
		 ture,	with  dimensions 2n×2m×2l.  Each subsequent mipmap has
		 dimensions 2i−1×2j−1×2k−1, where 2i×2j×2k are the  dimensions
		 of  the  previous  mipmap,  until either i=0, j=0 or k=0.  At
		 that point, subsequent mipmaps have dimension	1×2j−1×2k−1  ,
		 2i−1×1×2k−1  or 2i−1×2j−1×1 until the final mipmap, which has
		 dimension 1×1×1.  To define the mipmaps,  call	 glTexImage1D,
		 glTexImage2D, glTexImage3D, glCopyTexImage1D, or glCopyTexIm‐
		 age2D with the level argument indicating the  level-of-detail
		 number.  The  main texture image has a level-of-detail number
		 of 0.

		 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 eight 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
			   eight texture elements that are closest to the cen‐
			   ter 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
			   eight texture elements that are closest to the cen‐
			   ter	of  the pixel) to produce a texture value from
			   each mipmap.	 The final texture value is a weighted
			   average of those two values.

		 GL_FILTER4_SGIS
			   This filtering mode allows 1D and 2D textures to be
			   filtered using an application-defined, four	sample
			   per	dimension  filter.   Such filtering results in
			   higher image quality.  It is defined only for  non-
			   mipmapped  filters.	Because	 filter4  filtering is
			   defined only for non-mipmapped textures,  there  is
			   no  difference between its definition for minifica‐
			   tion and magnification. For more  information,  see
			   glTexFilterFuncSGIS.

		 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  four  or
		 eight	texture elements to determine the texture value of the
		 pixel being rendered and can produce more 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 tex‐
		 ture element.	It sets the texture magnification function  to
		 either GL_NEAREST, GL_LINEAR, GL_LINEAR_SHARPEN_SGIS, GL_LIN‐
		 EAR_SHARPEN_ALPHA_SGIS, or GL_LINEAR_SHARPEN_COLOR_SGIS  (see
		 below).  GL_NEAREST  is generally fastest, 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	eight  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_TEX‐
			   TURE_WRAP_R, and on the exact mapping.

		 GL_LINEAR_SHARPEN_SGIS
			   Samples  the	 levels 0 and 1 texture arrays exactly
			   as GL_LINEAR and extrapolate the red,  green,  blue
			   and	alpha  components  to  produce	the final red,
			   green, blue, and alpha components.

		 GL_LINEAR_SHARPEN_ALPHA_SGIS
			   Samples the levels 0 and 1 texture  arrays  exactly
			   as  GL_LINEAR and extrapolate only the alpha compo‐
			   nent. The red, green, and blue components are those
			   of level 0.

		 GL_LINEAR_SHARPEN_COLOR_SGIS
			   Samples  the	 levels 0 and 1 texture arrays exactly
			   as GL_LINEAR and extrapolate	 the  red,  green  and
			   blue	 components.  The  alpha  component is that of
			   level 0.  GL_FILTER4_SGIS Returns the Filter4  fil‐
			   tered  texture  element.  See GL_FILTER4_SGIS under
			   GL_TEXTURE_MIN_FILTER

       GL_TEXTURE_WRAP_S
		 Sets the wrap parameter for texture coordinate	 s  to	either
		 GL_CLAMP,  GL_CLAMP_TO_EDGE,  GL_REPEAT,  or GL_CLAMP_TO_BOR‐
		 DER_ARB.  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_EDGE
		 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_REPEAT causes the integer part of the s coordi‐
		 nate to be ignored; the GL uses  only	the  fractional	 part,
		 thereby  creating  a  repeating pattern.  Border texture ele‐
		 ments are accessed only  if  wrapping	is  set	 to  GL_CLAMP.
		 GL_CLAMP_TO_BORDER_ARB	 clamps	 texture coordinates such that
		 the texture filter always samples border texels for fragments
		 whose	corresponding  texture	coordinate is sufficiently far
		 outside the range [0,1].  The color returned when clamping is
		 derived  only from the border texels of the texture image, or
		 from the constant border color if the texture image does  not
		 have  a  border. Texture coordinates are clamped to the range
		 [min, max].  The minimum value is defined as min = -1	/  2N,
		 where	N  is  the  size  (not including borders) of the one-,
		 two-, or three-dimensional texture image in the direction  of
		 clamping.   The maximum value is defined as max = 1 - min, so
		 that clamping is always  symmetric  about  the	 [0,1]	mapped
		 range	of a texture coordinate.  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,  GL_CLAMP_TO_EDGE,  GL_REPEAT,  or GL_CLAMP_TO_BOR‐
		 DER_ARB.  See the discussion under  GL_TEXTURE_WRAP_S.	  Ini‐
		 tially, GL_TEXTURE_WRAP_T is set to GL_REPEAT.

       GL_TEXTURE_WRAP_R
		 Sets  the  wrap parameter for texture coordinate r of 3D tex‐
		 tures.	 See the  discussion  under  GL_TEXTURE_WRAP_S.	  Ini‐
		 tially, GL_TEXTURE_WRAP_R is set to GL_REPEAT.

       GL_TEXTURE_BORDER_COLOR
		 Sets  a  border color.	 params contains four values that com‐
		 prise the RGBA color of the texture  border.	Integer	 color
		 components  are interpreted linearly such that the most posi‐
		 tive 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  informa‐
		 tion.

       GL_POST_TEXTURE_FILTER_SCALE_SGIX
		 Specifies  the	 scale	values	with params set to an array of
		 four values.  The scale values can be queried using GetTexPa‐
		 rameterfv  or	GetTexParameteriv.   The  scale	 operation  is
		 applied directly before the  texture  environment  equations,
		 or, if the SGI_texture_color_table extension exists, directly
		 before the texture color lookup table.	 The four  values  for
		 scale	correspond to the R, G, B, and A scale factors.	 These
		 are applied to the corresponding texture components, Rt,  Gt,
		 Bt, and At, as denoted in the EXT_texture extension.  Follow‐
		 ing the scale and bias is a clamp to [0, 1].  The scale oper‐
		 ation	is effectively disabled by setting the four scale val‐
		 ues to 1.  There is no specific enable or disable  token  for
		 this extension.

       GL_POST_TEXTURE_FILTER_BIAS_SGIX
		 Specifies the bias values with params set to an array of four
		 values.  The bias values can be queried  using	 GetTexParame‐
		 terfv	or  GetTexParameteriv.	 The bias operation is applied
		 directly before the texture environment equations, or, if the
		 SGI_texture_color_table extension exists, directly before the
		 texture color lookup table, following	the  scale  operation.
		 The  four  values  for	 bias correspond to the R, G, B, and A
		 bias factors.	These are applied to the corresponding texture
		 components, Rt, Gt, Bt, and At, as denoted in the EXT_texture
		 extension.  Following the scale and bias is a	clamp  to  [0,
		 1].   The  bias  operation is effectively disabled by setting
		 the four bias values to 1.  There is no  specific  enable  or
		 disable token for this extension.

       GL_TEXTURE_MAX_ANISOTROPY_EXT
		 Specifies  the	 maximum  degree  of  anisotropy  needed, with
		 params set to an array of one	floating-point	value  greater
		 than  or  equal  to 1.0.  When the texture's value of GL_TEX‐
		 TURE_MAX_ANISOTROPY_EXT is equal to 1.0, the GL uses an  iso‐
		 tropic	 texture  filtering  approach.	However, when the tex‐
		 ture's value of TEXTURE_MAX_ANISOTROPY_EXT  is	 greater  than
		 1.0,  the  GL	implementation uses a texture filtering scheme
		 that accounts for a degree of anisotropy up to the smaller of
		 the  value of GL_TEXTURE_MAX_ANISTROPY_EXT or the implementa‐
		 tion-defined value of GL_MAX_TEXTURE_MAX_ANISTROPY_EXT.   The
		 anisotropic  texture  filtering scheme may only access mipmap
		 levels if  the	 minification  filter  is  one	that  requires
		 mipmaps.   Additionally, when a minification filter is speci‐
		 fied, the  anisotropic	 texture  filtering  scheme  may  only
		 access texture mipmap levels between the texture's values for
		 TEXTURE_BASE_LEVEL    and    TEXTURE_MAX_LEVEL,    inclusive.
		 GL_MAX_TEXTURE_MAX_ANISTROPY_EXT  can	be quieried using Get‐
		 Floatv command.

       GL_TEXTURE_MIN_LOD
		 Specifies the minimum level-of-detail number. If  the	calcu‐
		 lated	 level-of-detail   number   is	smaller	 than  GL_TEX‐
		 TURE_MIN_LOD, it is clamped  to  GL_TEXTURE_MIN_LOD.  Whether
		 the  minification  or magnification filter is used depends on
		 the clamped LOD value. The initial value is 0.

       GL_TEXTURE_MAX_LOD
		 Specifies the maximum level-of-detail number. If  the	calcu‐
		 lated	 level-of-detail   number   is	 larger	 than  GL_TEX‐
		 TURE_MIN_LOD, it is clamped to GL_TEXTURE_MAX_LOD The initial
		 value is 1000 and the permissible value is > 0.

       GL_TEXTURE_BASE_LEVEL
		 Specifies  the	 base  level-of-the  texture arrays. Level-of-
		 detail	 numbers  proceed  from	 GL_TEXTURE_BASE_LEVELfor  the
		 original  texture  array  through  p  = max {n,m,l} + GL_TEX‐
		 TURE_BASE_LEVEL. The initial value is 0 and  the  permissible
		 value is > 0.

       GL_TEXTURE_MAX_LEVEL
		 Specifies  the	 maximum  level-of-detail number.  The texture
		 arrays are defined from GL_TEXTURE_BASE_LEVEL through	min  {
		 p, GL_TEXTURE_MAX_LEVEL }.  The initial value is 1000 and the
		 permissible value is > 0.

       GL_TEXTURE_COMPARE_FUNC
		 Specifies  the	 texture  comparation	function   to	either
		 GL_LEQUAL, GL_GEQUAL, GL_LESS, GL_GREATER, GL_EQUAL, GL_NOTE‐
		 QUAL, GL_ALWAYS, or GL_NEVER.

       GL_TEXTURE_LOD_BIAS_S_SGIX
		 Specifies the bias applied to s in the level-of-detail calcu‐
		 lation.  The mipmapped textures can be made to appear sharper
		 or blurrier by supplying a negative or positive bias  respec‐
		 tively. The initial value is 0.

       GL_TEXTURE_LOD_BIAS_T_SGIX
		 Specifies the bias applied to t in the level-of-detail calcu‐
		 lation. The initial value is 0.

       GL_TEXTURE_LOD_BIAS_R_SGIX
		 Specifies the bias applied to r in the level-of-detail calcu‐
		 lation. The initial value is 0.

       GL_GENERATE_MIPMAP
		 Specifies  the	 side effect of modification of the base level
		 mipmap array. If enabled, any change made to the  base	 level
		 texture  will	trigger	 a  computation	 of  a complete set of
		 mipmap arrays. The initial value is FALSE.

NOTES
       Suppose that a program has enabled texturing (by calling glEnable  with
       argument	  GL_TEXTURE_1D,   GL_TEXTURE_2D,  GL_TEXTURE_3D,  or  GL_TEX‐
       TURE_CUBE_MAP) and has set GL_TEXTURE_MIN_FILTER to one	of  the	 func‐
       tions  that requires a mipmap.  If either the dimensions of the texture
       images currently defined (with previous calls to glTexImage1D, glTexIm‐
       age2D, glTexImage3D, glCopyTexImage1D, or glCopyTexImage2D) do not fol‐
       low 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 eight nearest texture elements in 3D tex‐
       tures, the four nearest texture elements in 2D textures,	 and  the  two
       nearest texture elements in 1D textures..

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.

       GL_INVALID_VALUE is generated if pname is  GL_DETAIL_TEXTURE_LEVEL_SGIS
       and param is positive or params points to a positive value.

       GL_INVALID_VALUE is generated when TexParameter is called with pname of
       TEXTURE_MAX_ANISOTROPY_EXT and a param value or value  of  what	params
       points to less than 1.0.

ASSOCIATED GETS
       glGetTexParameter
       glGetTexLevelParameter

SEE ALSO
       glBindTexture,	 glCopyPixels,	 glCopyTexImage1D,   glCopyTexImage2D,
       glCopyTexSubImage1D, glCopyTexSubImage2D, glCopyTexSubImage3D,  glDraw‐
       Pixels,	glPixelStore, glPixelTransfer, glPrioritizeTextures, glTexEnv,
       glTexGen, glTexImage1D,	glTexImage2D,  glTexImage3D,  glTexSubImage1D,
       glTexSubImage2D,	 glTexSubImage3D,  glSharpenTexFuncSGIS, glGetSharpen‐
       TexFuncSGIS.

				   6 June 01		   GLTEXPARAMETER(3gl)
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