glTexParameter man page on Tru64

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glTexParameter(3G)					    glTexParameter(3G)

NAME
       glTexParameter - set texture parameters

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

PARAMETERS
       Specifies  the  target  texture,	 which	must  be either GL_TEXTURE_1D,
       GL_TEXTURE_2D or GL_TEXTURE_3D.	Specifies the symbolic name of a  tex‐
       ture parameter.	pname can be one of the following: GL_TEXTURE_MIN_FIL‐
       TER,  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_TEX‐
       TURE_WRAP_T,  GL_TEXTURE_WRAP_R,	 GL_TEXTURE_BORDER_COLOR,  or  GL_TEX‐
       TURE_PRIORITY.  Specifies a pointer to an array where the value or val‐
       ues 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: The texture minifying function is used
       whenever the pixel being textured maps to an area greater than one tex‐
       ture  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	dimen‐
	      sions  2^n  x  2^m,  there  are  ( n, m ) + 1 mipmaps. The first
	      mipmap is the original texture, with dimensions 2^n X 2^m.  Each
	      subsequent  mipmap has dimensions 2^k - 1 x 2^l - 1, where 2^k x
	      2^l are the dimensions of the previous mipmap, until either k  =
	      0 or l = 0. At that point, subsequent mipmaps have dimension 1 x
	      2^l - 1 or 2^k - 1 x 1 until the final mipmap, which has	dimen‐
	      sion  1 x 1.  To define the mipmaps, call glTexImage1D, glTexIm‐
	      age2D, 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  x  1
	      mipmap.

	      params  supplies	a function for minifying the texture as one of
	      the following: Returns the value of the texture element that  is
	      nearest (in Manhattan distance) to the center of the pixel being
	      textured.	 Returns the weighted average of the four texture ele‐
	      ments  that  are	closest	 to the center of the pixel being tex‐
	      tured. 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.  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.  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.   Chooses  the	 two mipmaps that most closely
	      match the size of the pixel being textured and uses the GL_NEAR‐
	      EST  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.
	      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	 texture  ele‐
	      ments to determine the texture value of the pixel being rendered
	      and can produce moire patterns or ragged transitions.  The  ini‐
	      tial value of GL_TEXTURE_MIN_FILTER is GL_NEAREST_MIPMAP_LINEAR.
	      The texture magnification function is used when the pixel	 being
	      textured	maps to an area less than or equal to one texture ele‐
	      ment. 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.   Returns  the	 value	of the texture element that is
	      nearest (in Manhattan distance) to the center of the pixel being
	      textured.	 Returns the weighted average of the four texture ele‐
	      ments that are closest to the center of  the  pixel  being  tex‐
	      tured.  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.

       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.

       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.

       Specifies  the  index  of  the  lowest defined mipmap level. This is an
       integer value. The initial value is 0.

       Sets the index of the highest defined mipmap level. This is an  integer
       value. The initial value is 1000.

       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 arti‐
       facts when mapping a single image  onto	an  object.   GL_CLAMP_TO_EDGE
       causes  s  coordinates to be clamped to the range [ {1 over 2N}, 1 - {1
       over 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.  Border texture elements are accessed only if wrap‐
       ping is	set  to	 GL_CLAMP.  Initially,	GL_TEXTURE_WRAP_S  is  set  to
       GL_REPEAT.

       Sets  the  wrap	parameter for texture coordinate t to either GL_CLAMP,
       GL_CLAMP_TO_EDGE,  or  GL_REPEAT.  See  the  discussion	under  GL_TEX‐
       TURE_WRAP_S.  Initially,	 GL_TEXTURE_WRAP_T  is set to GL_REPEAT.  Sets
       the wrap	 parameter  for	 texture  coordinate  r	 to  either  GL_CLAMP,
       GL_CLAMP_TO_EDGE,  or  GL_REPEAT.  See  the  discussion	under  GL_TEX‐
       TURE_WRAP_S. Initially, GL_TEXTURE_WRAP_R is set to GL_REPEAT.  Sets  a
       border color.  params contains four values that comprise the RGBA color
       of the texture border. Integer color components	are  interpreted  lin‐
       early  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).  Specifies the texture residence priority of	 the  currently	 bound
       texture.	 Permissible values are in the range [0, 1]. See glPrioritize‐
       Textures and glBindTexture for more information.

NOTES
       GL_TEXTURE_3D,	 GL_TEXTURE_MIN_LOD,	GL_TEXTURE_MAX_LOD,    GL_TEX‐
       TURE_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,  glCopyTex‐
       Image1D,	 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.

       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.

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

PARAMETERS
       Specifies  the  target  texture,	 which	must  be either GL_TEXTURE_1D,
       GL_TEXTURE_2D, or GL_TEXTURE_3D.	 Specifies the symbolic name of a sin‐
       gle-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,  or  GL_TEX‐
       TURE_PRIORITY.  Specifies the value of pname.

ASSOCIATED GETS
       glGetTexParameter glGetTexLevelParameter

SEE ALSO
       glActiveTextureARB(3),  glBindTexture(3), glCopyPixels(3), glCopyTexIm‐
       age1D(3), glCopyTexImage2D(3), glCopyTexSubImage1D(3),  glCopyTexSubIm‐
       age2D(3),   glCopyTexSubImage3D(3),  glDrawPixels(3),  glPixelStore(3),
       glPixelTransfer(3), glPrioritizeTextures(3), glTexEnv(3),  glTexGen(3),
       glTexImage1D(3),	 glTexImage2D(3), glTexImage3D(3), glTexSubImage1D(3),
       (3), glTexSubImage2D(3glTexSubImage3D),

							    glTexParameter(3G)
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