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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glBeginTransformFeedback - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /></head><body><div class="refentry"><a id="glBeginTransformFeedback"></a><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 border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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 border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><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"><a id="parameters"></a><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"><a id="description"></a><h2>Description</h2><p>
Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader).
Transform feedback is said to be active after a call to <code class="function">glBeginTransformFeedback</code>
until a subsequent call to <a class="citerefentry" href="glEndTransformFeedback.xml"><span class="citerefentry"><span class="refentrytitle">glEndTransformFeedback</span></span></a>.
Transform feedback commands must be paired.
</p><p>
If no geometry shader is present, while transform feedback is active the <em class="parameter"><code>mode</code></em> parameter to
<a class="citerefentry" href="glDrawArrays.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a> must match those specified
in the following table:
</p><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 align="left" /><col align="left" /></colgroup><thead><tr><th style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left">
<span class="bold"><strong>
Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
</strong></span>
</th><th style="border-bottom: 2px solid ; " align="left">
<span class="bold"><strong>
Allowed Render Primitive <em class="parameter"><code>modes</code></em>
</strong></span>
</th></tr></thead><tbody><tr><td style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left"> <code class="constant">GL_POINTS</code> </td><td style="border-bottom: 2px solid ; " align="left"> <code class="constant">GL_POINTS</code> </td></tr><tr><td style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left"> <code class="constant">GL_LINES</code> </td><td style="border-bottom: 2px solid ; " align="left">
<code class="constant">GL_LINES</code>,
<code class="constant">GL_LINE_LOOP</code>,
<code class="constant">GL_LINE_STRIP</code>,
<code class="constant">GL_LINES_ADJACENCY</code>,
<code class="constant">GL_LINE_STRIP_ADJACENCY</code>
</td></tr><tr><td style="border-right: 2px solid ; " align="left">
<code class="constant">GL_TRIANGLES</code>
</td><td style="" align="left">
<code class="constant">GL_TRIANGLES</code>,
<code class="constant">GL_TRIANGLE_STRIP</code>,
<code class="constant">GL_TRIANGLE_FAN</code>,
<code class="constant">GL_TRIANGLES_ADJACENCY</code>,
<code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code>
</td></tr></tbody></table></div><p>
If a geometry shader is present, the output primitive type from the geometry shader must match those
provided in the following table:
</p><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 align="left" /><col align="left" /></colgroup><thead><tr><th style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left">
<span class="bold"><strong>
Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
</strong></span>
</th><th style="border-bottom: 2px solid ; " align="left">
<span class="bold"><strong>
Allowed Geometry Shader Output Primitive Type
</strong></span>
</th></tr></thead><tbody><tr><td style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left"> <code class="constant">GL_POINTS</code> </td><td style="border-bottom: 2px solid ; " align="left"> <code class="constant">points</code> </td></tr><tr><td style="border-right: 2px solid ; border-bottom: 2px solid ; " align="left"> <code class="constant">GL_LINES</code> </td><td style="border-bottom: 2px solid ; " align="left"> <code class="constant">line_strip</code> </td></tr><tr><td style="border-right: 2px solid ; " align="left"> <code class="constant">GL_TRIANGLES</code> </td><td style="" align="left"> <code class="constant">triangle_strip</code> </td></tr></tbody></table></div></div><div class="refsect1"><a id="notes"></a><h2>Notes</h2><p>
Geometry shaders, and the <code class="constant">GL_TRIANGLES_ADJACENCY</code>, <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code>,
<code class="constant">GL_LINES_ADJACENCY</code> and <code class="constant">GL_LINE_STRIP_ADJACENCY</code> primtive modes are available
only if the GL version is 3.2 or greater.
</p></div><div class="refsect1"><a id="errors"></a><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_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.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
if no geometry shader is present, transform feedback is active and <em class="parameter"><code>mode</code></em> is not one of the allowed modes.
</p><p>
<code class="constant">GL_INVALID_OPERATION</code> is generated by <a class="citerefentry" href="glDrawArrays.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
if a geometry shader is present, transform feedback is active and the output primitive type of the geometry shader does not
match the transform feedback <em class="parameter"><code>primitiveMode</code></em>.
</p><p>
<code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glEndTransformFeedback</code> if any binding
point used in transform feedback mode does not have a buffer object bound.
</p><p>
<code class="constant">GL_INVALID_OPERATION</code> is generated by <code class="function">glEndTransformFeedback</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><div class="refsect1"><a id="Copyright"></a><h2>Copyright</h2><p>
Copyright <span class="trademark"></span>© 2010-2013 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="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p></div></div></body></html>
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