Opentk/Source/Bind/Specifications/Docs/glDrawArraysIndirect.xml

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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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<refentry id="glDrawArraysIndirect">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>2010</year>
                <holder>Khronos Group.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glDrawTransformFeedback</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glDrawArraysIndirect</refname>
        <refpurpose>render primitives from array data, taking parameters from memory</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glDrawArraysIndirect</function></funcdef>
                <paramdef>GLenum <parameter>mode</parameter></paramdef>
                <paramdef>const void *<parameter>indirect</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <!-- eqn: ignoring delim $$ -->
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>mode</parameter></term>
            <listitem>
                <para>
                    Specifies what kind of primitives to render.
                    Symbolic constants
                    <constant>GL_POINTS</constant>,
                    <constant>GL_LINE_STRIP</constant>,
                    <constant>GL_LINE_LOOP</constant>,
                    <constant>GL_LINES</constant>,
                    <constant>GL_LINE_STRIP_ADJACENCY</constant>,
                    <constant>GL_LINES_ADJACENCY</constant>,
                    <constant>GL_TRIANGLE_STRIP</constant>,
                    <constant>GL_TRIANGLE_FAN</constant>,
                    <constant>GL_TRIANGLES</constant>,
                    <constant>GL_TRIANGLE_STRIP_ADJACENCY</constant>,
                    <constant>GL_TRIANGLES_ADJACENCY</constant>, and
                    <constant>GL_PATCHES</constant>
                    are accepted.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>indirect</parameter></term>
            <listitem>
                <para>
                    Specifies the address of a structure containing the draw parameters.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glDrawArraysIndirect</function> specifies multiple geometric primitives
            with very few subroutine calls. <function>glDrawArraysIndirect</function> behaves
            similarly to <citerefentry><refentrytitle>glDrawArraysInstanced</refentrytitle></citerefentry>,
            execpt that the parameters to <citerefentry><refentrytitle>glDrawArraysInstanced</refentrytitle></citerefentry>
            are stored in memory at the address given by <parameter>indirect</parameter>.
        </para>
        <para>
            The parameters addressed by <parameter>indirect</parameter> are packed into a structure
            that takes the form (in C):
            <programlisting><![CDATA[    typedef  struct {
        uint  count;
        uint  primCount;
        uint  first;
        uint  reservedMustBeZero;
    } DrawArraysIndirectCommand;

    const DrawArraysIndirectCommand  *cmd  = (const DrawArraysIndirectCommand  *)indirect;
    glDrawArraysInstanced(mode,  cmd->first,  cmd->count,  cmd->primCount);]]></programlisting>
        </para>
        <para>
            If a buffer is bound to the <constant>GL_INDIRECT_BUFFER</constant> binding at the time
            of a call to <function>glDrawArraysIndirect</function>, <parameter>indirect</parameter>
            is interpreted as an offset, in basic machine units, into that buffer and the parameter
            data is read from the buffer rather than from client memory.
        </para>
        <para>
            In contrast to <citerefentry><refentrytitle>glDrawArraysInstanced</refentrytitle></citerefentry>,
            the <code>first</code> member of the parameter structure is unsigned, and out-of-range indices
            do not generate an error. The results of the operation are undefined if the <code>reservedMustBeZero</code> member
            of the parameter structure is non-zero. However, no error is generated in this case.
        </para>
        <para>
            Vertex attributes that are modified by <function>glDrawArraysIndirect</function> have an
            unspecified value after <function>glDrawArraysIndirect</function> returns. Attributes that aren't
            modified remain well defined.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not an accepted value.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to an
            enabled array or to the <constant>GL_INDIRECT_BUFFER</constant> binding and the buffer object's data store is currently mapped.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if a geometry shader is active and <parameter>mode</parameter>
            is incompatible with the input primitive type of the geometry shader in the currently installed program object.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>mode</parameter> is <constant>GL_PATCHES</constant>
            and no tessellation control shader is active.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glDrawArrays</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDrawArraysInstanced</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDrawElements</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDrawRangeElements</refentrytitle></citerefentry>,
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 2010 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.
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
        </para>
    </refsect1>
</refentry>