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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glGetVertexAttrib">
    <info>
        <copyright>
            <year>2003-2005</year>
            <holder>3Dlabs Inc. Ltd.</holder>
        </copyright>
        <copyright>
            <year>2010-2013</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glGetVertexAttrib</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
    <refdescriptor>glGetVertexAttrib</refdescriptor>
        <refname>glGetVertexAttribdv</refname>
        <refname>glGetVertexAttribfv</refname>
        <refname>glGetVertexAttribiv</refname>
        <refname>glGetVertexAttribIiv</refname>
        <refname>glGetVertexAttribIuiv</refname>
        <refname>glGetVertexAttribLdv</refname>
        <refpurpose>Return a generic vertex attribute parameter</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
    <funcsynopsis>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribdv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLdouble *<parameter>params</parameter></paramdef>
        </funcprototype>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribfv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLfloat *<parameter>params</parameter></paramdef>
        </funcprototype>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribiv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLint *<parameter>params</parameter></paramdef>
        </funcprototype>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribIiv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLint *<parameter>params</parameter></paramdef>
        </funcprototype>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribIuiv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLuint *<parameter>params</parameter></paramdef>
        </funcprototype>
        <funcprototype>
        <funcdef>void <function>glGetVertexAttribLdv</function></funcdef>
        <paramdef>GLuint <parameter>index</parameter></paramdef>
        <paramdef>GLenum <parameter>pname</parameter></paramdef>
        <paramdef>GLdouble *<parameter>params</parameter></paramdef>
        </funcprototype>
    </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
    <variablelist>
        <varlistentry>
        <term><parameter>index</parameter></term>
        <listitem>
            <para>Specifies the generic vertex attribute
            parameter to be queried.</para>
        </listitem>
        </varlistentry>
        <varlistentry>
        <term><parameter>pname</parameter></term>
        <listitem>
            <para>Specifies the symbolic name of the vertex
            attribute parameter to be queried. Accepted values are
            <constant>GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_ENABLED</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_SIZE</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_STRIDE</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_TYPE</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_NORMALIZED</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_INTEGER</constant>,
            <constant>GL_VERTEX_ATTRIB_ARRAY_DIVISOR</constant>, or
            <constant>GL_CURRENT_VERTEX_ATTRIB</constant>.</para>
        </listitem>
        </varlistentry>
        <varlistentry>
        <term><parameter>params</parameter></term>
        <listitem>
            <para>Returns the requested data.</para>
        </listitem>
        </varlistentry>
    </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
    <para><function>glGetVertexAttrib</function> returns in
    <parameter>params</parameter> the value of a generic vertex
    attribute parameter. The generic vertex attribute to be queried
    is specified by <parameter>index</parameter>, and the parameter
    to be queried is specified by <parameter>pname</parameter>.</para>

    <para>The accepted parameter names are as follows:</para>

    <variablelist>
        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value, the name of the buffer object currently bound to
                    the binding point corresponding to generic vertex attribute array
                    <parameter>index</parameter>. If no buffer object is bound,
                    0 is returned. The initial value is 0.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_ENABLED</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value that is non-zero (true) if the vertex
            attribute array for <parameter>index</parameter> is
            enabled and 0 (false) if it is disabled. The initial
            value is <constant>GL_FALSE</constant>.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_SIZE</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value, the size of the vertex attribute array
            for <parameter>index</parameter>. The size is the
            number of values for each element of the vertex
            attribute array, and it will be 1, 2, 3, or 4. The
            initial value is 4.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_STRIDE</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value, the array stride for (number of bytes
            between successive elements in) the vertex attribute
            array for <parameter>index</parameter>. A value of 0
            indicates that the array elements are stored
            sequentially in memory. The initial value is 0.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_TYPE</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value, a symbolic constant indicating the
            array type for the vertex attribute array for
            <parameter>index</parameter>. Possible values are
            <constant>GL_BYTE</constant>,
            <constant>GL_UNSIGNED_BYTE</constant>,
            <constant>GL_SHORT</constant>,
            <constant>GL_UNSIGNED_SHORT</constant>,
            <constant>GL_INT</constant>,
            <constant>GL_UNSIGNED_INT</constant>,
            <constant>GL_FLOAT</constant>, and
            <constant>GL_DOUBLE</constant>. The initial value is
            <constant>GL_FLOAT</constant>.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_NORMALIZED</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value that is non-zero (true) if fixed-point
            data types for the vertex attribute array indicated
            by <parameter>index</parameter> are normalized when
            they are converted to floating point, and 0 (false)
            otherwise. The initial value is
            <constant>GL_FALSE</constant>.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_INTEGER</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value that is non-zero (true) if fixed-point
            data types for the vertex attribute array indicated
            by <parameter>index</parameter> have integer data types, and 0 (false)
            otherwise. The initial value is
            0 (<constant>GL_FALSE</constant>).</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_VERTEX_ATTRIB_ARRAY_DIVISOR</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns a
            single value that is the frequency divisor used for instanced
            rendering. See <citerefentry><refentrytitle>glVertexAttribDivisor</refentrytitle></citerefentry>.
            The initial value is 0.</para>
        </listitem>
        </varlistentry>

        <varlistentry>
        <term><constant>GL_CURRENT_VERTEX_ATTRIB</constant></term>
        <listitem>
                <para>
                </para>
            <para> <parameter>params</parameter> returns four
            values that represent the current value for the
            generic vertex attribute specified by index. Generic
            vertex attribute 0 is unique in that it has no
            current state, so an error will be generated if
            <parameter>index</parameter> is 0. The initial value
            for all other generic vertex attributes is
            (0,0,0,1).</para>
            <para>
                <function>glGetVertexAttribdv</function> and <function>glGetVertexAttribfv</function>
                return the current attribute values as four single-precision floating-point values;
                <function>glGetVertexAttribiv</function> reads them as floating-point values and
                converts them to four integer values; <function>glGetVertexAttribIiv</function> and
                <function>glGetVertexAttribIuiv</function> read and return them as signed or unsigned
                integer values, respectively; <function>glGetVertexAttribLdv</function> reads and returns
                them as four double-precision floating-point values.
            </para>
        </listitem>
        </varlistentry>
    </variablelist>

    <para>All of the parameters except <constant>GL_CURRENT_VERTEX_ATTRIB</constant>
    represent state stored in the currently bound vertex array object.</para>

    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
    <para>If an error is generated, no change is made to the
    contents of <parameter>params</parameter>.</para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
    <para><constant>GL_INVALID_OPERATION</constant> is generated if <parameter>pname</parameter>
    is not <constant>GL_CURRENT_VERTEX_ATTRIB</constant> and there is no
    currently bound vertex array object.</para>

    <para><constant>GL_INVALID_VALUE</constant> is generated if
    <parameter>index</parameter> is greater than or equal to
    <constant>GL_MAX_VERTEX_ATTRIBS</constant>.</para>

    <para><constant>GL_INVALID_ENUM</constant> is generated if
    <parameter>pname</parameter> is not an accepted value.</para>

    <para><constant>GL_INVALID_OPERATION</constant> is generated if
    <parameter>index</parameter> is 0 and
    <parameter>pname</parameter> is
    <constant>GL_CURRENT_VERTEX_ATTRIB</constant>.</para>
    </refsect1>
    <refsect1 xml:id="associatedgets"><title>Associated Gets</title>
    <para><citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
    with argument <constant>GL_MAX_VERTEX_ATTRIBS</constant></para>

    <para><citerefentry><refentrytitle>glGetVertexAttribPointerv</refentrytitle></citerefentry>
    with arguments <parameter>index</parameter> and
    <constant>GL_VERTEX_ATTRIB_ARRAY_POINTER</constant></para>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
    <para><citerefentry><refentrytitle>glBindAttribLocation</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glDisableVertexAttribArray</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glEnableVertexAttribArray</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glVertexAttrib</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glVertexAttribDivisor</refentrytitle></citerefentry>,
    <citerefentry><refentrytitle>glVertexAttribPointer</refentrytitle></citerefentry></para>
    </refsect1>
    <refsect1 xml:id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"/> 2003-2005 3Dlabs Inc. Ltd.
            Copyright <trademark class="copyright"/> 2010-2013 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>
