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

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

<div class="refnamediv">

<h2>Name</h2>

<p>glBeginTransformFeedback — start transform feedback operation</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">glBeginTransformFeedback</strong>(</code>

</td>

<td>GLenum <var class="pdparam">primitiveMode</var><code>)</code>;</td>

</tr>

</table>

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

</div>

<div class="funcsynopsis">

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

<tr>

<td>

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

</td>

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

</tr>

</table>

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

</div>

</div>

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

<h2>Parameters for <code class="function">glBeginTransformFeedback</code></h2>

<div class="variablelist">

<dl class="variablelist">

<dt>

<span class="term">

<em class="parameter">

<code>primitiveMode</code>

</em>

</span>

</dt>

<dd>

<p>

Specify the output type of the primitives that will be recorded into the

buffer objects that are bound for transform feedback.

</p>

</dd>

</dl>

</div>

</div>

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

<h2>Description</h2>

<p>

Transform feedback mode captures the values of varying variables written by the vertex shader.

Transform feedback is said to be active after a call to <code class="function">glBeginTransformFeedback</code>

until a subsequent call to <code class="function">glEndTransformFeedback</code>.

Transform feedback commands must be paired. An implicit <a class="citerefentry" href="glResumeTransformFeedback"><span class="citerefentry"><span class="refentrytitle">glResumeTransformFeedback</span></span></a>

is performed by <code class="function">glEndTransformFeedback</code> if the transform feedback is paused.

Transform feedback is restricted to non-indexed <code class="constant">GL_POINTS</code>, <code class="constant">GL_LINES</code>, and

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

</p>

<p>

While transform feedback is active the <em class="parameter"><code>mode</code></em> parameter to

<a class="citerefentry" href="glDrawArrays"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a> must exactly match the

<em class="parameter"><code>primitiveMode</code></em> specified by <code class="function">glBeginTransformFeedback</code>.

</p>

</div>

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

<h2>Errors</h2>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginTransformFeedback</code> is executed

while transform feedback is active.

</p>

<p>

<code class="constant">GL_INVALID_ENUM</code> is generated by <code class="function">glBeginTransformFeedback</code> if <em class="parameter"><code>primitiveMode</code></em>

is not one of <code class="constant">GL_POINTS</code>, <code class="constant">GL_LINES</code>, or <code class="constant">GL_TRIANGLES</code>.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glEndTransformFeedback</code> is executed

while transform feedback is not active.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated by <a class="citerefentry" href="glDrawArrays"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>

and <a class="citerefentry" href="glDrawArraysInstanced"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstanced</span></span></a> if transform feedback is active

and <em class="parameter"><code>mode</code></em> does not exactly match <em class="parameter"><code>primitiveMode</code></em>.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated by <a class="citerefentry" href="glDrawElements"><span class="citerefentry"><span class="refentrytitle">glDrawElements</span></span></a>,

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

<a class="citerefentry" href="glDrawRangeElements"><span class="citerefentry"><span class="refentrytitle">glDrawRangeElements</span></span></a> if transform feedback is active and not paused.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glBeginTransformFeedback</code> if any binding

point used in transform feedback mode does not have a buffer object bound. In interleaved mode, only the first buffer

object binding point is ever written to.

</p>

<p>

<code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glBeginTransformFeedback</code> if no binding

points would be used, either because no program object is active of because the active program object has specified

no varying variables to record.

</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 ; border-bottom: 2px solid ; ">

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

</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="function">glEndTransformFeedback</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="glPauseTransformFeedback"><span class="citerefentry"><span class="refentrytitle">glPauseTransformFeedback</span></span></a>,

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