gluBuild1DMipmaps(3G)	       OpenGL Reference		 gluBuild1DMipmaps(3G)



NAME
     gluBuild1DMipmaps - builds	1-D mipmaps


C SPECIFICATION
     GLint gluBuild1DMipmaps( GLenum target,
			      GLint component,
			      GLsizei width,
			      GLenum format,
			      GLenum type,
			      const void *data )


PARAMETERS
     target	Specifies the target texture.  Must be GL_TEXTURE_1D.

     component	Specifies the number of	color components in the	texture.  Must
		be 1, 2, 3, or 4 or one	of the following symbolic constants:
		GL_ALPHA, GL_INTENSITY_EXT, GL_LUMINANCE, GL_LUMINANCE_ALPHA,
		GL_RGB,	GL_RGBA.

     width	Specifies the width in pixels of the texture image.

     format	Specifies the format of	the pixel data.	 Must be one of:
		GL_COLOR_INDEX,	GL_RED,	GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB,
		GL_RGBA, GL_LUMINANCE, GL_LUMINANCE_ALPHA and GL_ABGR_EXT.

     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_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT,
		GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT,
		and GL_UNSIGNED_INT_10_10_10_2_EXT.

     data	Specifies a pointer to the image data in memory.



DESCRIPTION
     gluBuild1DMipmaps builds a	series of prefiltered 1-D texture maps of
     decreasing	resolutions called mipmaps. These are used for the
     antialiasing of texture mapped primitives.

     A return value of 0 indicates success. Otherwise a	GLU error code is
     returned (see gluErrorString).

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



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gluBuild1DMipmaps(3G)	       OpenGL Reference		 gluBuild1DMipmaps(3G)



     Then, proxy textures (see glTexImage1D) are used to determine if the
     implementation can	fit the	requested texture. If not, width is
     continually halved	until it fits.

     Next, a series of mipmaps is built	by decimating a	copy of	data in	half
     until size	1 is reached. At each level, each texel	in the halved mipmap
     is	an average of the corresponding	two texels in the larger mipmap.

     glTexImage1D is called to load each of these mipmaps by level.  Level 0
     is	a copy of data.	The highest level is log2(width).  For example,	if
     width is 64 and the implementation	can store a texture of this size, the
     following mipmaps are built: 64x1,	32x1, 16x1, 8x1, 4x1, 2x1 and 1x1.
     These correspond to levels	0 through 6, respectively.

     Please refer to the glTexImage1D reference	page for a description of the
     acceptable	values for the type parameter. See the glDrawPixels reference
     page for a	description of the acceptable values for the data parameter.

NOTES
     Note that there is	no direct way of querying the maximum level. This can
     be	queried	indirectly via glGetTexLevelParameter. First, query for	the
     width actually used at level 0. (The width	may be <= width	since proxy
     textures might have strunk	it to fit the implementation.)	Then the
     maximum level can be derived from the formula log2(width).

ERRORS
     GLU_INVALID_VALUE is returned if width is < 1.

     GLU_INVALID_ENUM is returned if format or type are	not legal.

     GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_BYTE_3_3_2_EXT	and
     format is not GL_RGB.

     GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_SHORT_4_4_4_4_EXT and
     format is neither GL_RGBA nor GL_ABGR_EXT.

     GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_SHORT_5_5_5_1_EXT and
     format is neither GL_RGBA nor GL_ABGR_EXT.

     GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_INT_8_8_8_8_EXT and
     format is neither GL_RGBA nor GL_ABGR_EXT.

     GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_INT_10_10_10_2_EXT
     and format	is neither GL_RGBA nor GL_ABGR_EXT.

BUGS
     Passing GL_STENCIL_INDEX or GL_DEPTH_COMPONENT as format will incorrectly
     return 0 and set the error	code to	GL_INVALID_ENUM. It should return
     GLU_INVALID_ENUM and not set an error code.






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gluBuild1DMipmaps(3G)	       OpenGL Reference		 gluBuild1DMipmaps(3G)



SEE ALSO
     glDrawPixels, glTexImage1D, glTexImage2D, gluBuild2DMipmaps,
     gluErrorString, glGetTexImage, glGetTexLevelParameter.




















































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