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GLUBUILD2DMIPMAPS(3G)					 GLUBUILD2DMIPMAPS(3G)

NAME
       gluBuild2DMipmaps - builds a two-dimensional mipmap

C SPECIFICATION
       GLint gluBuild2DMipmaps( GLenum target,
				GLint internalFormat,
				GLsizei width,
				GLsizei height,
				GLenum format,
				GLenum type,
				const void *data )

PARAMETERS
       target	       Specifies the target texture.  Must be GL_TEXTURE_2D.

       internalFormat  Requests	 the  internal	storage	 of the texture image.
		       The most current version of the SGI  implementation  of
		       GLU does not check this value for validity before pass‐
		       ing it on to the underlying OpenGL  implementation.   A
		       value that is not accepted by the OpenGL implementation
		       will lead to an	OpenGL	error.	 The  benefit  of  not
		       checking	 this  value  at  the GLU level is that OpenGL
		       extensions can add new internal texture formats without
		       requiring  a revision of the GLU implementation.	 Older
		       implementations of GLU check this value and raise a GLU
		       error  if it is not 1, 2, 3, or 4 or one of the follow‐
		       ing symbolic constants: GL_ALPHA, GL_ALPHA4, GL_ALPHA8,
		       GL_ALPHA12,  GL_ALPHA16,	 GL_LUMINANCE,	GL_LUMINANCE4,
		       GL_LUMINANCE8,	  GL_LUMINANCE12,      GL_LUMINANCE16,
		       GL_LUMINANCE_ALPHA,		 GL_LUMINANCE4_ALPHA4,
		       GL_LUMINANCE6_ALPHA2,		 GL_LUMINANCE8_ALPHA8,
		       GL_LUMINANCE12_ALPHA4,	       GL_LUMINANCE12_ALPHA12,
		       GL_LUMINANCE16_ALPHA16,	GL_INTENSITY,	GL_INTENSITY4,
		       GL_INTENSITY8,  GL_INTENSITY12, GL_INTENSITY16, GL_RGB,
		       GL_R3_G3_B2,  GL_RGB4,  GL_RGB5,	  GL_RGB8,   GL_RGB10,
		       GL_RGB12,   GL_RGB16,   GL_RGBA,	  GL_RGBA2,  GL_RGBA4,
		       GL_RGB5_A1,   GL_RGBA8,	 GL_RGB10_A2,	GL_RGBA12   or
		       GL_RGBA16.

       width, height   Specifies in pixels the width and height, respectively,
		       of the texture image.

       format	       Specifies the  of the  pixel  data.   Must  be  one  of
		       GL_COLOR_INDEX,	GL_DEPTH_COMPONENT,  GL_RED, GL_GREEN,
		       GL_BLUE, GL_ALPHA, GL_RGB,  GL_RGBA,  GL_BGR,  GL_BGRA,
		       GL_LUMINANCE, or GL_LUMINANCE_ALPHA.

       type	       Specifies  the  data  type  for	data.	Must be one of
		       GL_UNSIGNED_BYTE,	  GL_BYTE,	    GL_BITMAP,
		       GL_UNSIGNED_SHORT,  GL_SHORT,  GL_UNSIGNED_INT, GL_INT,
		       GL_FLOAT,		       GL_UNSIGNED_BYTE_3_3_2,
		       GL_UNSIGNED_BYTE_2_3_3_REV,    GL_UNSIGNED_SHORT_5_6_5,
		       GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4,
		       GL_UNSIGNED_SHORT_4_4_4_4_REV,
		       GL_UNSIGNED_SHORT_5_5_5_1,
		       GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,
		       GL_UNSIGNED_INT_8_8_8_8_REV,
		       GL_UNSIGNED_INT_10_10_10_2,			    or
		       GL_UNSIGNED_INT_2_10_10_10_REV.

       data	       Specifies a pointer to the image data in memory.

DESCRIPTION
       gluBuild2DMipmaps builds a series of prefiltered	 two-dimensional  tex‐
       ture  maps  of decreasing resolutions called a mipmap. This is used for
       the antialiasing of texture-mapped primitives.

       A return value of zero indicates success, otherwise a GLU error code is
       returned (see gluErrorString).

       Initially,  the width and height of data are checked to see if they are
       a power of 2. If not, a copy of data (not data), is scaled up  or  down
       to  the	nearest	 power	of  2.	This  copy will be used for subsequent
       mipmapping operations described below. (If width or height  is  exactly
       between	powers	of  2, then the copy of data will scale upwards.)  For
       example, if width is 57 and height is 23 then a copy of data will scale
       up  to  64  in  width  and down to 16 in depth, before mipmapping takes
       place.

       Then, proxy textures (see glTexImage2D) are used to  determine  if  the
       implementation  can  fit the requested texture. If not, both dimensions
       are continually halved until it fits. (If the OpenGL version is ≤  1.0,
       both  maximum  texture  dimensions are clamped to the value returned by
       glGetIntegerv with the argument GL_MAX_TEXTURE_SIZE.)

       Next, a series of mipmap levels is built by decimating a copy  of  data
       in half along both dimensions until size 1×1 is reached. At each level,
       each texel in the halved mipmap level is an average of the  correspond‐
       ing four texels in the larger mipmap level. (In the case of rectangular
       images, the decimation will ultimately reach an N×1 or  1×N  configura‐
       tion. Here, two texels are averaged instead.)

       glTexImage2D is called to load each of these mipmap levels.  Level 0 is
       a copy of data.	The highest  level  is	log2(max(width,height)).   For
       example,	 if  width  is	64 and height is 16 and the implementation can
       store a texture of this size, the following mipmap  levels  are	built:
       64×16,  32×8, 16×4, 8×2, 4×1, 2×1 and 1×1. These correspond to levels 0
       through 6, respectively.

       See the glTexImage1D reference page for a description of the acceptable
       values  for format parameter. See the glDrawPixels reference page for a
       description of the acceptable values for type parameter.

NOTES
       Note that there is no direct way of querying the	 maximum  level.  This
       can  be derived indirectly via glGetTexLevelParameter. First, query for
       the width and height actually used at level 0.  (The width  and	height
       may  not be equal to width and height respectively since proxy textures
       might have scaled them to fit the implementation.)   Then  the  maximum
       level can be derived from the formula log2(max(width,height)).

NOTES
       Formats	 GL_BGR,   and	 GL_BGRA,  and	types  GL_UNSIGNED_BYTE_3_3_2,
       GL_UNSIGNED_BYTE_2_3_3_REV,		      GL_UNSIGNED_SHORT_5_6_5,
       GL_UNSIGNED_SHORT_5_6_5_REV,		    GL_UNSIGNED_SHORT_4_4_4_4,
       GL_UNSIGNED_SHORT_4_4_4_4_REV,		    GL_UNSIGNED_SHORT_5_5_5_1,
       GL_UNSIGNED_SHORT_1_5_5_5_REV,		      GL_UNSIGNED_INT_8_8_8_8,
       GL_UNSIGNED_INT_8_8_8_8_REV,	 GL_UNSIGNED_INT_10_10_10_2,	   and
       GL_UNSIGNED_INT_2_10_10_10_REV  are only available if the GL version is
       1.2 or greater and if the GLU version is 1.3 or greater.

ERRORS
       GLU_INVALID_VALUE is returned if width, or height is < 1.

       GLU_INVALID_ENUM is returned if internalFormat, format, or type is  not
       legal.

       GLU_INVALID_OPERATION  is returned if type is GL_UNSIGNED_BYTE_3_3_2 or
       GL_UNSIGNED_BYTE_2_3_3_REV and format is not GL_RGB.

       GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_5_6_5 or
       GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.

       GLU_INVALID_OPERATION  is returned if type is GL_UNSIGNED_SHORT_4_4_4_4
       or GL_UNSIGNED_SHORT_4_4_4_4_REV and  format  is	 neither  GL_RGBA  nor
       GL_BGRA.

       GLU_INVALID_OPERATION  is returned if type is GL_UNSIGNED_SHORT_5_5_5_1
       or GL_UNSIGNED_SHORT_1_5_5_5_REV and  format  is	 neither  GL_RGBA  nor
       GL_BGRA.

       GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_8_8_8_8 or
       GL_UNSIGNED_INT_8_8_8_8_REV and format is neither GL_RGBA nor GL_BGRA.

       GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_10_10_10_2
       or  GL_UNSIGNED_INT_2_10_10_10_REV  and	format	is neither GL_RGBA nor
       GL_BGRA.

SEE ALSO
       glDrawPixels(3G), glTexImage1D(3G), glTexImage2D(3G), glTexImage3D(3G),
       gluBuild1DMipmaps(3G),	 gluBuild3DMipmaps(3G),	   gluErrorString(3G),
       glGetTexImage(3G),			   glGetTexLevelParameter(3G),
       gluBuild1DMipmapLevels(3G),		   gluBuild2DMipmapLevels(3G),
       gluBuild3DMipmapLevels(3G)

							 GLUBUILD2DMIPMAPS(3G)
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