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GLTEXPARAMETER(3G)					    GLTEXPARAMETER(3G)

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,   which   must   be	either
	       GL_TEXTURE_1D, GL_TEXTURE_2D, or GL_TEXTURE_3D.

       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_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, or GL_TEXTURE_PRIORITY.

       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,   which   must   be	either
	      GL_TEXTURE_1D, GL_TEXTURE_2D or GL_TEXTURE_3D.

       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_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,
	      or GL_TEXTURE_PRIORITY.

       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) 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_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 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−1, 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_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 tex‐
		 ture elements to determine the texture	 value	of  the	 pixel
		 being rendered and can produce moire patterns or ragged tran‐
		 sitions.   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 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 tex‐
		 ture  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_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_BASE_LEVEL
		 Specifies  the index of the lowest defined mipmap level. This
		 is an integer value. The initial value is 0.

       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_WRAP_S
		 Sets  the  wrap  parameter for texture coordinate s to either
		 GL_CLAMP, GL_CLAMP_TO_EDGE, 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_EDGE causes s coordinates to be
		 clamped to the range ⎣__,1−__⎦, 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 pat‐
		 tern.	Border texture elements are accessed only if  wrapping
		 is  set  to GL_CLAMP.	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, 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, GL_CLAMP_TO_EDGE, or GL_REPEAT.  See the discussion
		 under GL_TEXTURE_WRAP_S.  Initially, 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.

NOTES
       GL_TEXTURE_3D,	      GL_TEXTURE_MIN_LOD,	   GL_TEXTURE_MAX_LOD,
       GL_TEXTURE_BASE_LEVEL,  and  GL_TEXTURE_MAX_LEVEL are only available if
       the GL version is 1.2 or greater.

       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 dif‐
       fering 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.

       When  the  GL_ARB_multitexture  extension  is supported, glTexParameter
       specifies the texture parameters for the active texture unit, specified
       by calling glActiveTextureARB.

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

SEE ALSO
       glActiveTextureARB(3G),	    glBindTexture(3G),	     glCopyPixels(3G),
       glCopyTexImage1D(3G),   glCopyTexImage2D(3G),  glCopyTexSubImage1D(3G),
       glCopyTexSubImage2D(3G),	  glCopyTexSubImage3D(3G),   glDrawPixels(3G),
       glPixelStore(3G),     glPixelTransfer(3G),    glPrioritizeTextures(3G),
       glTexEnv(3G),   glTexGen(3G),	glTexImage1D(3G),    glTexImage2D(3G),
       glTexImage3D(3G),       glTexSubImage1D(3G),	  glTexSubImage2D(3G),
       glTexSubImage3D(3G)

							    GLTEXPARAMETER(3G)
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