<div class="refentry" id="glDrawElementsIndirect">

<div class="titlepage"></div>

<div class="refnamediv">

<h2>Name</h2>

<p>glDrawElementsIndirect — render indexed primitives from array data, taking parameters from memory</p>

</div>

<div class="refsynopsisdiv">

<h2>C Specification</h2>

<div class="funcsynopsis">

<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">

<tr>

<td>

<code class="funcdef">void <strong class="fsfunc">glDrawElementsIndirect</strong>(</code>

</td>

<td>GLenum <var class="pdparam">mode</var>, </td>

</tr>

<tr>

<td> </td>

<td>GLenum <var class="pdparam">type</var>, </td>

</tr>

<tr>

<td> </td>

<td>const void *<var class="pdparam">indirect</var><code>)</code>;</td>

</tr>

</table>

<div class="funcprototype-spacer"> </div>

</div>

</div>

<div class="refsect1" id="parameters">

<h2>Parameters</h2>

<div class="variablelist">

<dl class="variablelist">

<dt>

<span class="term">

<em class="parameter">

<code>mode</code>

</em>

</span>

</dt>

<dd>

<p>

Specifies what kind of primitives to render.

Symbolic constants

<code class="constant">GL_POINTS</code>,

<code class="constant">GL_LINE_STRIP</code>,

<code class="constant">GL_LINE_LOOP</code>,

<code class="constant">GL_LINES</code>,

<code class="constant">GL_TRIANGLE_STRIP</code>,

<code class="constant">GL_TRIANGLE_FAN</code>, and

<code class="constant">GL_TRIANGLES</code>,

are accepted.

</p>

</dd>

<dt>

<span class="term">

<em class="parameter">

<code>type</code>

</em>

</span>

</dt>

<dd>

<p>

Specifies the type of data in the buffer bound to the <code class="constant">GL_ELEMENT_ARRAY_BUFFER</code> binding.

</p>

</dd>

<dt>

<span class="term">

<em class="parameter">

<code>indirect</code>

</em>

</span>

</dt>

<dd>

<p>

Specifies the address of a structure containing the draw parameters.

</p>

</dd>

</dl>

</div>

</div>

<div class="refsect1" id="description">

<h2>Description</h2>

<p>

<code class="function">glDrawElementsIndirect</code> specifies multiple indexed geometric primitives

with very few subroutine calls. <code class="function">glDrawElementsIndirect</code> behaves

similarly to <a class="citerefentry" href="glDrawElementsInstanced"><span class="citerefentry"><span class="refentrytitle">glDrawElementsInstanced</span></span></a>,

except that the parameters to <a class="citerefentry" href="glDrawElementsInstanced"><span class="citerefentry"><span class="refentrytitle">glDrawElementsInstanced</span></span></a>

are stored in memory at the address given by <em class="parameter"><code>indirect</code></em> and the <span class="emphasis"><em>i</em></span>th element

transferred by the corresponding draw call will be taken from element <em class="parameter"><code>indices</code></em>[i] + <em class="parameter"><code>baseVertex</code></em>

of each enabled array. If the resulting value is larger than the maximum value representable by <em class="parameter"><code>type</code></em>,

it is as if the calculation were upconverted to 32-bit unsigned integers (with wrapping on overflow conditions).

The operation is undefined if the sum would be negative.It also supports the addition of

a value baseVertex to each index.

</p>

<p>

The parameters addressed by <em class="parameter"><code>indirect</code></em> are packed into a structure

that takes the form (in C):

</p>

<pre class="programlisting"> typedef struct {

uint count;

uint instanceCount;

uint firstIndex;

int baseVertex;

uint reservedMustBeZero;

} DrawElementsIndirectCommand;</pre>

<p>

<code class="function">glDrawElementsIndirect</code> is equivalent to:

</p>

<p>

<pre class="programlisting"> void glDrawElementsIndirect(GLenum mode, GLenum type, const void * indirect)

{

const DrawElementsIndirectCommand *cmd = (const DrawElementsIndirectCommand *)indirect;

glDrawElementsInstancedBaseVertex(mode,

cmd-&gt;count,

type,

cmd-&gt;firstIndex * size-of-type,

cmd-&gt;instanceCount,

cmd-&gt;baseVertex);

}</pre>

<p>

</p>

<p>

If a buffer is bound to the <code class="constant">GL_DRAW_INDIRECT_BUFFER</code> binding at the time

of a call to <code class="function">glDrawElementsIndirect</code>, <em class="parameter"><code>indirect</code></em>

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.

</p>

<p>

Note that indices stored in client memory are not supported. If no buffer is bound to the

<code class="constant">GL_ELEMENT_ARRAY_BUFFER</code> binding, an error will be generated.

</p>

<p>

The results of the operation are undefined if the <code class="code">reservedMustBeZero</code> member

of the parameter structure is non-zero. However, no error is generated in this case.

</p>

<p>

Vertex attributes that are modified by <code class="function">glDrawElementsIndirect</code> have an

unspecified value after <code class="function">glDrawElementsIndirect</code> returns. Attributes that aren't

modified remain well defined.

</p>

</div>

<div class="refsect1" id="notes">

<h2>Notes</h2>

<p>

<code class="function">glDrawElementsInstancedBaseVertex</code> isn't actually present in OpenGL ES, but is used to describe this functionality.

</p>

</div>

<div class="refsect1" id="errors">

<h2>Errors</h2>

<p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not an accepted value.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if no buffer is bound to the <code class="constant">GL_ELEMENT_ARRAY_BUFFER</code>

binding, or if such a buffer's data store is currently mapped.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to an

enabled array or to the <code class="constant">GL_DRAW_INDIRECT_BUFFER</code> binding and the buffer object's data store is currently mapped.

</p>

</div>

{$pipelinestall}{$examples}

<div class="refsect1" id="versions">

<h2>API Version Support</h2>

<div class="informaltable">

<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">

<colgroup>

<col style="text-align: left; "/>

<col style="text-align: center; " class="firstvers"/>

<col style="text-align: center; "/>

<col style="text-align: center; " class="lastvers"/>

</colgroup>

<thead>

<tr>

<th style="text-align: left; border-right: 2px solid ; ">

</th>

<th style="text-align: center; border-bottom: 2px solid ; " colspan="3">

<span class="bold"><strong>OpenGL ES API Version</strong></span>

</th>

</tr>

<tr>

<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>Function Name</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>2.0</strong></span>

</th>

<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">

<span class="bold"><strong>3.0</strong></span>

</th>

<th style="text-align: center; border-bottom: 2px solid ; ">

<span class="bold"><strong>3.1</strong></span>

</th>

</tr>

</thead>

<tbody>

<tr>

<td style="text-align: left; border-right: 2px solid ; ">

<code class="function">glDrawElementsIndirect</code>

</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; border-right: 2px solid ; ">-</td>

<td style="text-align: center; ">✔</td>

</tr>

</tbody>

</table>

</div>

</div>

<div class="refsect1" id="seealso">

<h2>See Also</h2>

<p>

<a class="citerefentry" href="glDrawArrays"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>,

<a class="citerefentry" href="glDrawArraysInstanced"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstanced</span></span></a>,

<a class="citerefentry" href="glDrawArraysIndirect"><span class="citerefentry"><span class="refentrytitle">glDrawArraysIndirect</span></span></a>,

<a class="citerefentry" href="glDrawElements"><span class="citerefentry"><span class="refentrytitle">glDrawElements</span></span></a>,

<a class="citerefentry" href="glDrawRangeElements"><span class="citerefentry"><span class="refentrytitle">glDrawRangeElements</span></span></a>,

</p>

</div>

<div class="refsect1" id="Copyright">

<h2>Copyright</h2>

<p>

Copyright © 2010-2014 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.

<a class="link" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p>

</div>

</div>