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

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

<div class="refnamediv">

<h2>Name</h2>

<p>gl_PrimitiveID — contains the index of the current primitive</p>

</div>

<div class="refsynopsisdiv">

<h2>Declaration</h2>

<p>

</p>

<pre class="programlisting">// In tessellation control, tessellation evaluation, and

// fragment shaders</pre>

<p>

<code class="fieldsynopsis"><span class="modifier">in </span><span class="type">int </span><span class="varname">gl_PrimitiveID </span>;</code>

</p>

<p>

</p>

<pre class="programlisting">// In geometry shaders</pre>

<p>

<code class="fieldsynopsis"><span class="modifier">out </span><span class="type">int </span><span class="varname">gl_PrimitiveID </span>;</code>

</p>

</div>

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

<h2>Description</h2>

<p>

<code class="varname">gl_PrimitiveID</code> is a tessellation control, tessellation evaluation

and fragment language input variable. For the tessellation control and tessellation

evaluation languages, it holds the number of primitives processed by

the shader since the current set of rendering primitives was started. The first

primitive processed by the drawing command is numbered zero and the primitive ID counter is incremented after every individual point, line

or triangle primitive is processed. For triangles drawn in point or line mode, the

primitive ID counter is incremented only once, even through multiple points or lines

may actually be drawn. Restarting a primitive topology using the primitive restart

index has no effect on the primitive ID counter.

</p>

<p>

In the geometry language, <code class="varname">gl_PrimitiveID</code> is an output

variable that is passed to the corresponding <code class="varname">gl_PrimitiveID</code> input

variable in the fragment shader. If no geomery shader is present then <code class="varname">gl_PrimitiveID</code>

in the fragment language behaves identically as it would in the tessellation control and evaluation

languages. If a geometry shader is present but does not write to <code class="varname">gl_PrimitiveID</code>,

the value of <code class="varname">gl_PrimitiveID</code> in the fragment shader is undefined.

</p>

</div>

{$pipelinestall}{$examples}

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

<h2>Version Support</h2>

<div class="informaltable">

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<colgroup>

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

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

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<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="12">

<span class="bold"><strong>OpenGL Shading Language 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>1.10</strong></span>

</th>

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

<span class="bold"><strong>1.20</strong></span>

</th>

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

<span class="bold"><strong>1.30</strong></span>

</th>

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

<span class="bold"><strong>1.40</strong></span>

</th>

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

<span class="bold"><strong>1.50</strong></span>

</th>

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

<span class="bold"><strong>3.30</strong></span>

</th>

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

<span class="bold"><strong>4.00</strong></span>

</th>

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

<span class="bold"><strong>4.10</strong></span>

</th>

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

<span class="bold"><strong>4.20</strong></span>

</th>

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

<span class="bold"><strong>4.30</strong></span>

</th>

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

<span class="bold"><strong>4.40</strong></span>

</th>

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

<span class="bold"><strong>4.50</strong></span>

</th>

</tr>

</thead>

<tbody>

<tr>

<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "><code class="varname">gl_PrimitiveID</code> (Fragment and Geometry Languages)</td>

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

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

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

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

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

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

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

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

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

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

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

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

</tr>

<tr>

<td style="text-align: left; border-right: 2px solid ; "><code class="varname">gl_PrimitiveID</code> (Tessellation Control and Evaluation Languages)</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; border-right: 2px solid ; ">-</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; border-right: 2px solid ; ">-</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; border-right: 2px solid ; ">✔</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="gl_InstanceID"><span class="citerefentry"><span class="refentrytitle">gl_InstanceID</span></span></a>,

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

<a class="citerefentry" href="gl_PrimitiveIDIn"><span class="citerefentry"><span class="refentrytitle">gl_PrimitiveIDIn</span></span></a>

</p>

</div>

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

<h2>Copyright</h2>

<p>

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.

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

</p>

</div>

</div>