
<refentry id="gluBuild2DMipmaps">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>gluBuild2DMipmaps</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>gluBuild2DMipmaps</refname>
        <refpurpose>builds a two-dimensional mipmap</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>GLint <function>gluBuild2DMipmaps</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLint <parameter>internalFormat</parameter></paramdef>
                <paramdef>GLsizei <parameter>width</parameter></paramdef>
                <paramdef>GLsizei <parameter>height</parameter></paramdef>
                <paramdef>GLenum <parameter>format</parameter></paramdef>
                <paramdef>GLenum <parameter>type</parameter></paramdef>
                <paramdef>const void * <parameter>data</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>target</parameter></term>
            <listitem>
                <para>
                    Specifies the target texture.  Must be <constant>GLU_TEXTURE_2D</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>internalFormat</parameter></term>
            <listitem>
                <para>
                    Requests the internal storage format 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:
                    <constant>GLU_ALPHA</constant>,
                    <constant>GLU_ALPHA4</constant>,
                    <constant>GLU_ALPHA8</constant>,
                    <constant>GLU_ALPHA12</constant>,
                    <constant>GLU_ALPHA16</constant>,
                    <constant>GLU_LUMINANCE</constant>,
                    <constant>GLU_LUMINANCE4</constant>,
                    <constant>GLU_LUMINANCE8</constant>,
                    <constant>GLU_LUMINANCE12</constant>,
                    <constant>GLU_LUMINANCE16</constant>,
                    <constant>GLU_LUMINANCE_ALPHA</constant>,
                    <constant>GLU_LUMINANCE4_ALPHA4</constant>,
                    <constant>GLU_LUMINANCE6_ALPHA2</constant>,
                    <constant>GLU_LUMINANCE8_ALPHA8</constant>,
                    <constant>GLU_LUMINANCE12_ALPHA4</constant>,
                    <constant>GLU_LUMINANCE12_ALPHA12</constant>,
                    <constant>GLU_LUMINANCE16_ALPHA16</constant>,
                    <constant>GLU_INTENSITY</constant>,
                    <constant>GLU_INTENSITY4</constant>,
                    <constant>GLU_INTENSITY8</constant>,
                    <constant>GLU_INTENSITY12</constant>,
                    <constant>GLU_INTENSITY16</constant>,
                    <constant>GLU_RGB</constant>,
                    <constant>GLU_R3_G3_B2</constant>,
                    <constant>GLU_RGB4</constant>,
                    <constant>GLU_RGB5</constant>,
                    <constant>GLU_RGB8</constant>,
                    <constant>GLU_RGB10</constant>,
                    <constant>GLU_RGB12</constant>,
                    <constant>GLU_RGB16</constant>,
                    <constant>GLU_RGBA</constant>,
                    <constant>GLU_RGBA2</constant>,
                    <constant>GLU_RGBA4</constant>,
                    <constant>GLU_RGB5_A1</constant>,
                    <constant>GLU_RGBA8</constant>,
                    <constant>GLU_RGB10_A2</constant>,
                    <constant>GLU_RGBA12</constant>, or
                    <constant>GLU_RGBA16</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>width</parameter></term>
            <term><parameter>height</parameter></term>
            <listitem>
                <para>
                    Specifies in pixels the width and height, respectively, of the texture image. 
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>format</parameter></term>
            <listitem>
                <para>
                    Specifies the format of the pixel data.
                    Must be one of
                    <constant>GLU_COLOR_INDEX</constant>,
                    <constant>GLU_DEPTH_COMPONENT</constant>,
                    <constant>GLU_RED</constant>,
                    <constant>GLU_GREEN</constant>,
                    <constant>GLU_BLUE</constant>,
                    <constant>GLU_ALPHA</constant>,
                    <constant>GLU_RGB</constant>,
                    <constant>GLU_RGBA</constant>,
                    <constant>GLU_BGR</constant>,
                    <constant>GLU_BGRA</constant>,
                    <constant>GLU_LUMINANCE</constant>, or
                    <constant>GLU_LUMINANCE_ALPHA</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>type</parameter></term>
            <listitem>
                <para>
                    Specifies the data type for <parameter>data</parameter>.
                    Must be one of
                    <constant>GLU_UNSIGNED_BYTE</constant>,
                    <constant>GLU_BYTE</constant>,
                    <constant>GLU_BITMAP</constant>,
                    <constant>GLU_UNSIGNED_SHORT</constant>,
                    <constant>GLU_SHORT</constant>,
                    <constant>GLU_UNSIGNED_INT</constant>,
                    <constant>GLU_INT</constant>, 
                    <constant>GLU_FLOAT</constant>, 
                    <constant>GLU_UNSIGNED_BYTE_3_3_2</constant>,
                    <constant>GLU_UNSIGNED_BYTE_2_3_3_REV</constant>,
                    <constant>GLU_UNSIGNED_SHORT_5_6_5</constant>,
                    <constant>GLU_UNSIGNED_SHORT_5_6_5_REV</constant>,
                    <constant>GLU_UNSIGNED_SHORT_4_4_4_4</constant>,
                    <constant>GLU_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
                    <constant>GLU_UNSIGNED_SHORT_5_5_5_1</constant>,
                    <constant>GLU_UNSIGNED_SHORT_1_5_5_5_REV</constant>,
                    <constant>GLU_UNSIGNED_INT_8_8_8_8</constant>,
                    <constant>GLU_UNSIGNED_INT_8_8_8_8_REV</constant>,
                    <constant>GLU_UNSIGNED_INT_10_10_10_2</constant>, or
                    <constant>GLU_UNSIGNED_INT_2_10_10_10_REV</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>data</parameter></term>
            <listitem>
                <para>
                    Specifies a pointer to the image data in memory.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>gluBuild2DMipmaps</function> builds a series of prefiltered two-dimensional texture maps of decreasing
            resolutions called a mipmap. This is used for the antialiasing of
            texture-mapped primitives.
        </para>
        <para>
            A return value of zero indicates success, otherwise a GLU error code is
            returned (see <citerefentry><refentrytitle>gluErrorString</refentrytitle></citerefentry>).
        </para>
        <para>
            Initially, the <parameter>width</parameter> and <parameter>height</parameter> of <parameter>data</parameter> are checked to see if they
            are a power of 2. If not, a copy of <parameter>data</parameter> (not <parameter>data</parameter>), is scaled up
            or down to the nearest power of 2. This copy will be used for subsequent
            mipmapping operations described below. (If <parameter>width</parameter> or <parameter>height</parameter> is exactly
            between powers of 2, then the copy of <parameter>data</parameter> will scale upwards.)  For
            example, if <parameter>width</parameter> is 57 and <parameter>height</parameter> is 23, then a copy of <parameter>data</parameter> will
            scale up to 64 in <parameter>width</parameter> and down to 16 in depth, before mipmapping takes
            place.
        </para>
        <para>
            Then, proxy textures (see <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>) 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 \(&lt;= 1.0,
            both maximum texture dimensions are clamped to the value returned
            by <citerefentry><refentrytitle>glGetIntegerv</refentrytitle></citerefentry> with the argument <constant>GLU_MAX_TEXTURE_SIZE</constant>.)
        </para>
        <para>
            Next, a series of mipmap levels is built by decimating a copy of <parameter>data</parameter>
            in half along both dimensions until size 
            <inlineequation><mml:math>
                <!-- eqn: 1  times  1:-->
                <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>
            is reached. At
            each level,
            each texel in the halved mipmap level is an average of the corresponding
            four texels in the larger mipmap level. (In the case of rectangular
            images, the decimation will ultimately reach an 
            <inlineequation><mml:math>
                <!-- eqn: N  times  1:-->
                <mml:mrow>
                    <mml:mi mathvariant="italic">N</mml:mi>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>
            or
            <inlineequation><mml:math>
                <!-- eqn: 1  times  N:-->
                <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mi mathvariant="italic">N</mml:mi>
                </mml:mrow>
            </mml:math></inlineequation>
            configuration. Here, two texels are averaged instead.)
        </para>
        <para>
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> is called to load each of these mipmap levels.
            Level 0 is a copy of <parameter>data</parameter>.  The highest level is
            <inlineequation><mml:math>
                <!-- eqn: {log sub 2} ( max (width,height)):-->
                <mml:mrow>
                    <mml:mfenced open="" close="">
                        <mml:msub><mml:mi mathvariant="italic">log</mml:mi>
                        <mml:mn>2</mml:mn>
                        </mml:msub>
                    </mml:mfenced>
                    <mml:mo>&af;</mml:mo>
                    <mml:mfenced open="(" close=")">
                        <mml:mrow>
                            <mml:mi mathvariant="italic">max</mml:mi>
                            <mml:mo>&af;</mml:mo>
                            <mml:mfenced open="(" close=")">
                                <mml:mi mathvariant="italic">width</mml:mi>
                                <mml:mi mathvariant="italic">height</mml:mi>
                            </mml:mfenced>
                        </mml:mrow>
                    </mml:mfenced>
                </mml:mrow>
            </mml:math></inlineequation>.
            For example,
            if <parameter>width</parameter> is 64 and <parameter>height</parameter> is 16
            and the implementation can store a texture of this size, the following
            mipmap levels are built: 
            <inlineequation><mml:math>
                <!-- eqn: 64  times  16:-->
                <mml:mrow>
                    <mml:mn>64</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>16</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>, 
            <inlineequation><mml:math>
                <!-- eqn: 32  times  8:-->
                <mml:mrow>
                    <mml:mn>32</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>8</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>, 
            <inlineequation><mml:math>
                <!-- eqn: 16  times  4:-->
                <mml:mrow>
                    <mml:mn>16</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>4</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>,
            <inlineequation><mml:math>
                <!-- eqn: 8  times  2:-->
                <mml:mrow>
                    <mml:mn>8</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>2</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>, 
            <inlineequation><mml:math>
                <!-- eqn: 4  times  1:-->
                <mml:mrow>
                    <mml:mn>4</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>, 
            <inlineequation><mml:math>
                <!-- eqn: 2  times  1:-->
                <mml:mrow>
                    <mml:mn>2</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>,
            and 
            <inlineequation><mml:math>
                <!-- eqn: 1  times  1:-->
                <mml:mrow>
                    <mml:mn>1</mml:mn>
                    <mml:mo>&times;</mml:mo>
                    <mml:mn>1</mml:mn>
                </mml:mrow>
            </mml:math></inlineequation>
            These
            correspond to levels 0 through 6, respectively.
        </para>
        <para>
            See the <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry> reference page for a description of the
            acceptable values for <parameter>format</parameter> parameter. See the <citerefentry><refentrytitle>glDrawPixels</refentrytitle></citerefentry> 
            reference page for a description of the acceptable values 
            for <parameter>type</parameter> parameter.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            Note that there is no direct way of querying the maximum level. This can
            be derived indirectly via <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry>. First, query
            for the width and height actually used at level 0.  (The width and
            height may not be equal to <parameter>width</parameter> and <parameter>height</parameter> respectively since proxy
            textures might have scaled them to fit the implementation.)  Then the
            maximum level can be derived from the formula
            <inlineequation><mml:math>
                <!-- eqn: {log sub 2}( max (width,height)):-->
                <mml:mrow>
                    <mml:mfenced open="" close="">
                        <mml:msub><mml:mi mathvariant="italic">log</mml:mi>
                        <mml:mn>2</mml:mn>
                        </mml:msub>
                    </mml:mfenced>
                    <mml:mo>&af;</mml:mo>
                    <mml:mfenced open="(" close=")">
                        <mml:mrow>
                            <mml:mi mathvariant="italic">max</mml:mi>
                            <mml:mo>&af;</mml:mo>
                            <mml:mfenced open="(" close=")">
                                <mml:mi mathvariant="italic">width</mml:mi>
                                <mml:mi mathvariant="italic">height</mml:mi>
                            </mml:mfenced>
                        </mml:mrow>
                    </mml:mfenced>
                </mml:mrow>
            </mml:math></inlineequation>.
        </para>
        <para>
            Formats <constant>GLU_BGR</constant>, and <constant>GLU_BGRA</constant>, and types 
            <constant>GLU_UNSIGNED_BYTE_3_3_2</constant>,
            <constant>GLU_UNSIGNED_BYTE_2_3_3_REV</constant>,
            <constant>GLU_UNSIGNED_SHORT_5_6_5</constant>,
            <constant>GLU_UNSIGNED_SHORT_5_6_5_REV</constant>,
            <constant>GLU_UNSIGNED_SHORT_4_4_4_4</constant>,
            <constant>GLU_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
            <constant>GLU_UNSIGNED_SHORT_5_5_5_1</constant>,
            <constant>GLU_UNSIGNED_SHORT_1_5_5_5_REV</constant>,
            <constant>GLU_UNSIGNED_INT_8_8_8_8</constant>,
            <constant>GLU_UNSIGNED_INT_8_8_8_8_REV</constant>,
            <constant>GLU_UNSIGNED_INT_10_10_10_2</constant>, and
            <constant>GLU_UNSIGNED_INT_2_10_10_10_REV</constant> are only available if the GL version 
            is 1.2 or greater and if the GLU version is 1.3 or greater.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GLU_INVALID_VALUE</constant> is returned if <parameter>width</parameter> or <parameter>height</parameter> is &lt; 1.
        </para>
        <para>
            <constant>GLU_INVALID_ENUM</constant> is returned if <parameter>internalFormat</parameter>, <parameter>format</parameter>, or <parameter>type</parameter> is not 
            legal.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_BYTE_3_3_2</constant> or <constant>GLU_UNSIGNED_BYTE_2_3_3_REV</constant>
            and <parameter>format</parameter> is not <constant>GLU_RGB</constant>.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_SHORT_5_6_5</constant> or <constant>GLU_UNSIGNED_SHORT_5_6_5_REV</constant>
            and <parameter>format</parameter> is not <constant>GLU_RGB</constant>.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_SHORT_4_4_4_4</constant> or <constant>GLU_UNSIGNED_SHORT_4_4_4_4_REV</constant>
            and <parameter>format</parameter> is neither <constant>GLU_RGBA</constant> nor <constant>GLU_BGRA</constant>.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_SHORT_5_5_5_1</constant> or <constant>GLU_UNSIGNED_SHORT_1_5_5_5_REV</constant>
            and <parameter>format</parameter> is neither <constant>GLU_RGBA</constant> nor <constant>GLU_BGRA</constant>.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_INT_8_8_8_8</constant> or <constant>GLU_UNSIGNED_INT_8_8_8_8_REV</constant>
            and <parameter>format</parameter> is neither <constant>GLU_RGBA</constant> nor <constant>GLU_BGRA</constant>.
        </para>
        <para>
            <constant>GLU_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is <constant>GLU_UNSIGNED_INT_10_10_10_2</constant> or <constant>GLU_UNSIGNED_INT_2_10_10_10_REV</constant>
            and <parameter>format</parameter> is neither <constant>GLU_RGBA</constant> nor <constant>GLU_BGRA</constant>.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>gluBuild1DMipmapLevels</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>gluBuild1DMipmaps</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>gluBuild2DMipmapLevels</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>gluBuild3DMipmapLevels</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>gluBuild3DMipmaps</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>gluErrorString</refentrytitle></citerefentry>, 
            <citerefentry><refentrytitle>glDrawPixels</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetTexImage</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, 
            <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
        </para>
    </refsect1>
</refentry>
