'\" e
'\"! eqn | mmdoc
'\"macro stdmacro
.ds Vn Version 1.2
.ds Dt 6 March 1997
.ds Re Release 1.2.0
.ds Dp May 02 11:53
.ds Dm 37 build1dmi
.ds Xs 40806 9 build1dmipmaps.gl
.TH GLUBUILD1DMIPMAPS 3G
.SH NAME
.B "gluBuild1DMipmaps
\- builds a one-dimensional mipmap

.SH C SPECIFICATION
GLint \f3gluBuild1DMipmaps\fP(
GLenum \fItarget\fP,
.nf
.ta \w'\f3GLint \fPgluBuild1DMipmaps( 'u
	GLint \fIinternalFormat\fP,
	GLsizei \fIwidth\fP,
	GLenum \fIformat\fP,
	GLenum \fItype\fP,
	const void \fI*data\fP )
.fi

.EQ
delim $$
.EN
.SH PARAMETERS
.TP \w'\fIinternalFormat\fP\ \ 'u 
\f2target\fP
Specifies the target texture.  Must be \%\f3GL_TEXTURE_1D\fP.
.TP
\f2internalFormat\fP
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 passing 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 following
symbolic constants:
\%\f3GL_ALPHA\fP,
\%\f3GL_ALPHA4\fP,
\%\f3GL_ALPHA8\fP,
\%\f3GL_ALPHA12\fP,
\%\f3GL_ALPHA16\fP,
\%\f3GL_LUMINANCE\fP,
\%\f3GL_LUMINANCE4\fP,
\%\f3GL_LUMINANCE8\fP,
\%\f3GL_LUMINANCE12\fP,
\%\f3GL_LUMINANCE16\fP,
\%\f3GL_LUMINANCE_ALPHA\fP,
\%\f3GL_LUMINANCE4_ALPHA4\fP,
\%\f3GL_LUMINANCE6_ALPHA2\fP,
\%\f3GL_LUMINANCE8_ALPHA8\fP,
\%\f3GL_LUMINANCE12_ALPHA4\fP,
\%\f3GL_LUMINANCE12_ALPHA12\fP,
\%\f3GL_LUMINANCE16_ALPHA16\fP,
\%\f3GL_INTENSITY\fP,
\%\f3GL_INTENSITY4\fP,
\%\f3GL_INTENSITY8\fP,
\%\f3GL_INTENSITY12\fP,
\%\f3GL_INTENSITY16\fP,
\%\f3GL_RGB\fP,
\%\f3GL_R3_G3_B2\fP,
\%\f3GL_RGB4\fP,
\%\f3GL_RGB5\fP,
\%\f3GL_RGB8\fP,
\%\f3GL_RGB10\fP,
\%\f3GL_RGB12\fP,
\%\f3GL_RGB16\fP,
\%\f3GL_RGBA\fP,
\%\f3GL_RGBA2\fP,
\%\f3GL_RGBA4\fP,
\%\f3GL_RGB5_A1\fP,
\%\f3GL_RGBA8\fP,
\%\f3GL_RGB10_A2\fP,
\%\f3GL_RGBA12\fP, or
\%\f3GL_RGBA16\fP.
.TP
\f2width\fP
Specifies the width, in pixels, of the texture image. 
.TP
\f2format\fP
Specifies the  of the pixel data.
Must be one of
\%\f3GL_COLOR_INDEX\fP,
\%\f3GL_DEPTH_COMPONENT\fP,
\%\f3GL_RED\fP,
\%\f3GL_GREEN\fP,
\%\f3GL_BLUE\fP,
\%\f3GL_ALPHA\fP,
\%\f3GL_RGB\fP,
\%\f3GL_RGBA\fP,
\%\f3GL_BGR\fP,
\%\f3GL_BGRA\fP,
\%\f3GL_LUMINANCE\fP, 
\%\f3GL_LUMINANCE_ALPHA\fP.
.TP
\f2type\fP
Specifies the data type for \f2data\fP.
Must be one of
\%\f3GL_UNSIGNED_BYTE\fP,
\%\f3GL_BYTE\fP,
\%\f3GL_BITMAP\fP,
\%\f3GL_UNSIGNED_SHORT\fP,
\%\f3GL_SHORT\fP,
\%\f3GL_UNSIGNED_INT\fP,
\%\f3GL_INT\fP, 
\%\f3GL_FLOAT\fP, 
\%\f3GL_UNSIGNED_BYTE_3_3_2\fP,
\%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP,
\%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP,
\%\f3GL_UNSIGNED_INT_10_10_10_2\fP, or
\%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP.
.TP
\f2data\fP
Specifies a pointer to the image data in memory.
.SH DESCRIPTION
\%\f3gluBuild1DMipmaps\fP builds a series of prefiltered one-dimensional texture maps of decreasing
resolutions called a mipmap. This is used for the antialiasing of
texture mapped primitives.
.P
A return value of zero indicates success, otherwise a GLU error code is
returned (see \%\f3gluErrorString\fP).
.P
Initially, the \f2width\fP of \f2data\fP is checked to see if it is
a power of 2. If not, a copy of \f2data\fP is scaled up or down to the
nearest power of 2. (If \f2width\fP is exactly between powers of 2, then
the copy of \f2data\fP will scale upwards.)  This copy will be used for
subsequent mipmapping operations described below. 
For example, if \f2width\fP is 57 then a copy of \f2data\fP
will scale up to 64 before mipmapping
takes place.
.P
Then, proxy textures (see \f3glTexImage1D\fP) are used to determine if
the implementation can fit the requested texture. If not, \f2width\fP is
continually halved until it fits.
.P
Next, a series of mipmap levels is built by decimating a copy of
\f2data\fP in half
until size $1 ~times~ 1$ is reached. At each level, each texel in the
halved mipmap level is an average of the corresponding two texels in the larger
mipmap level.
.P
\f3glTexImage1D\fP is called to load each of these mipmap levels.
Level 0 is a copy of \f2data\fP. 
The highest level is ${log sub 2}(\f2width\fP)$.
For example, if \f2width\fP is 64 and the implementation can store a texture of
this size, the following mipmap levels are
built: $64 ~times~ 1$, $32 ~times~ 1$, $16 ~times~ 1$, $8 ~times~ 1$,
$4 ~times~ 1$, $2 ~times~ 1$ and $1 ~times~ 1$. These correspond to 
levels 0 through 6, respectively.
.P
See the \f3glTexImage1D\fP reference page for a description of the
acceptable values for the \f2type\fP parameter. See the \f3glDrawPixels\fP 
reference page for a description of the acceptable values 
for the \f2data\fP parameter.
.SH NOTES
Note that there is no direct way of querying the maximum level. This can
be derived indirectly via \f3glGetTexLevelParameter\fP. First, query
for the
width actually used at level 0. 
(The width may not be equal to \f2width\fP since
proxy textures might have scaled it to fit the implementation.)
Then the maximum
level can be derived from the formula ${log sub 2}(\f2width\fP)$.
.P
Formats \%\f3GL_BGR\fP, and \%\f3GL_BGRA\fP, and types 
\%\f3GL_UNSIGNED_BYTE_3_3_2\fP,
\%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5\fP,
\%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP,
\%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP,
\%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP,
\%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8\fP,
\%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP,
\%\f3GL_UNSIGNED_INT_10_10_10_2\fP, and
\%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP are only available if the GL version 
is 1.2 or greater, and if the GLU version is 1.3 or greater.
.SH ERRORS
\%\f3GLU_INVALID_VALUE\fP is returned if \f2width\fP is < 1.
.P
\%\f3GLU_INVALID_ENUM\fP is returned if \f2format\fP or \f2type\fP are not legal.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_BYTE_3_3_2\fP or \%\f3GL_UNSIGNED_BYTE_2_3_3_REV\fP
and \f2format\fP is not \%\f3GL_RGB\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_5_6_5\fP or \%\f3GL_UNSIGNED_SHORT_5_6_5_REV\fP
and \f2format\fP is not \%\f3GL_RGB\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_4_4_4_4\fP or \%\f3GL_UNSIGNED_SHORT_4_4_4_4_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_SHORT_5_5_5_1\fP or \%\f3GL_UNSIGNED_SHORT_1_5_5_5_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_INT_8_8_8_8\fP or \%\f3GL_UNSIGNED_INT_8_8_8_8_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.P
\%\f3GLU_INVALID_OPERATION\fP is returned if \f2type\fP is \%\f3GL_UNSIGNED_INT_10_10_10_2\fP or \%\f3GL_UNSIGNED_INT_2_10_10_10_REV\fP
and \f2format\fP is neither \%\f3GL_RGBA\fP nor \%\f3GL_BGRA\fP.
.SH SEE ALSO
\f3glDrawPixels(3G)\fP,
\f3glTexImage1D(3G)\fP,
\f3glTexImage2D(3G)\fP, 
\f3glTexImage3D(3G)\fP,
\%\f3gluBuild2DMipmaps(3G)\fP,
\%\f3gluBuild3DMipmaps(3G)\fP,
\%\f3gluErrorString(3G)\fP, 
\f3glGetTexImage(3G)\fP,
\f3glGetTexLevelParameter(3G)\fP, 
\%\f3gluBuild1DMipmapLevels(3G)\fP,
\%\f3gluBuild2DMipmapLevels(3G)\fP, 
\%\f3gluBuild3DMipmapLevels(3G)\fP