Opentk/Source/Bind/Specifications/Docs/glDrawArraysIndirect.xml
2010-12-04 21:51:40 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<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>