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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glTexStorage2D">
    <info>
        <copyright>
            <year>2011-2014</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glTexStorage2D</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glTexStorage2D</refname>
        <refpurpose>simultaneously specify storage for all levels of a two-dimensional texture</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glTexStorage2D</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLsizei <parameter>levels</parameter></paramdef>
                <paramdef>GLenum <parameter>internalformat</parameter></paramdef>
                <paramdef>GLsizei <parameter>width</parameter></paramdef>
                <paramdef>GLsizei <parameter>height</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>target</parameter></term>
            <listitem>
                <para>
                    Specify the target of the operation. <parameter>target</parameter> must be
                    one of <constant>GL_TEXTURE_2D</constant>,
                    or <constant>GL_TEXTURE_CUBE_MAP</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>levels</parameter></term>
            <listitem>
                <para>
                    Specify the number of texture levels.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>internalformat</parameter></term>
            <listitem>
                <para>
                    Specifies the sized internal format to be used to store texture image data.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>width</parameter></term>
            <listitem>
                <para>
                    Specifies the width of the texture, in texels.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>height</parameter></term>
            <listitem>
                <para>
                    Specifies the height of the texture, in texels.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            <function>glTexStorage2D</function> specifies the storage requirements for all levels
            of a two-dimensional texture simultaneously. Once a texture is specified with this
            command, the format and dimensions of all levels become immutable.
                        The contents of the image may still be modified, however, its storage requirements
            may not change. Such a texture is referred to as an <emphasis>immutable-format</emphasis>
            texture.
        </para>
        <para>
            The behavior of <function>glTexStorage2D</function> depends on the <parameter>target</parameter> parameter.
            When <parameter>target</parameter> is <constant>GL_TEXTURE_2D</constant>,
            calling <function>glTexStorage2D</function> is equivalent, assuming no errors are generated,
            to executing the following pseudo-code:
        </para>
<programlisting>    for (i = 0; i &lt; levels; i++)
    {
        glTexImage2D(target, i, internalformat, width, height, 0, format, type, NULL);
        width = max(1, (width / 2));
        height = max(1, (height / 2));
    }</programlisting>
        <para>
            When <parameter>target</parameter> is <constant>GL_TEXTURE_CUBE_MAP</constant>, <function>glTexStorage2D</function>
            is equivalent to:
        </para>
<programlisting>    for (i = 0; i &lt; levels; i++)
    {
        for (face in (+X, -X, +Y, -Y, +Z, -Z))
        {
            glTexImage2D(face, i, internalformat, width, height, 0, format, type, NULL);
        }
        width = max(1, (width / 2));
        height = max(1, (height / 2));
    }</programlisting>
        <para>
            Since no texture data is actually provided, the values used in the pseudo-code
            for <parameter>format</parameter> and <parameter>type</parameter> are
            irrelevant and may be considered to be any values that are legal for the
            chosen <parameter>internalformat</parameter> enumerant. <parameter>internalformat</parameter>
            must be one of the sized internal formats given in Table 1, or one of the compressed internal
                        formats given in Table 2 below. Upon success,
            the value of <constant>GL_TEXTURE_IMMUTABLE_FORMAT</constant> becomes
            <constant>GL_TRUE</constant>. The value of <constant>GL_TEXTURE_IMMUTABLE_FORMAT</constant>
            may be discovered by calling <citerefentry><refentrytitle>glGetTexParameter</refentrytitle></citerefentry>
            with <parameter>pname</parameter> set to <constant>GL_TEXTURE_IMMUTABLE_FORMAT</constant>.
            No further changes to the dimensions or format of the texture object may be
            made. Using any command that might alter the dimensions or format of the
            texture object (such as <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> or
            another call to <function>glTexStorage2D</function>) will result in the
            generation of a <constant>GL_INVALID_OPERATION</constant> error, even if it
            would not, in fact, alter the dimensions or format of the object.
        </para>
        <para>
            <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="internalformattable.xml"/>
        </para>
        <para>
            <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="compressedformattable.xml"/>
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if the default texture object is curently bound to <parameter>target</parameter>.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if the texture object curently bound to <parameter>target</parameter>
                        already has <constant>GL_TEXTURE_IMMUTABLE_FORMAT</constant> set to <constant>GL_TRUE</constant>.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not a
            valid sized internal format.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not
            one of the accepted target enumerants.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if <parameter>width</parameter>, <parameter>height</parameter> or
                        <parameter>levels</parameter> are less than 1.
        </para>

        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>levels</parameter> is greater than
            <inlineequation>
                <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                  <mml:mrow>
                    <mml:mfenced open="&lfloor;" close="&rfloor;">
                      <mml:mrow>
                        <mml:msub>
                          <mml:mi>log</mml:mi>
                          <mml:mn>2</mml:mn>
                        </mml:msub>
                        <mml:mfenced open="(" close=")">
                          <mml:mrow>
                            <mml:mi>max</mml:mi>
                            <mml:mfenced open="(" close=")">
                              <mml:mrow>
                                <mml:mi>width</mml:mi>
                                <mml:mo>,</mml:mo>
                                <mml:mtext fontfamily="Times New Roman">&nbsp;</mml:mtext>
                                <mml:mi>height</mml:mi>
                              </mml:mrow>
                            </mml:mfenced>
                          </mml:mrow>
                        </mml:mfenced>
                      </mml:mrow>
                    </mml:mfenced>
                    <mml:mo>+</mml:mo>
                    <mml:mn>1</mml:mn>
                  </mml:mrow>
                </mml:math>
            </inlineequation>.
    </para>
    </refsect1>
    <refsect1 xml:id="versions">
        <title>API Version Support</title>
        <informaltable>
            <tgroup cols="3" align="left">
                <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
                <tbody>
                    <row>
                        <entry>glTexStorage2D</entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es30']/*)"/>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCompressedTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexStorage3D</refentrytitle></citerefentry>.
        </para>
    </refsect1>
    <refsect1 xml:id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"/> 2011-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
        </para>
    </refsect1>
</refentry>
