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+<?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</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="glBeginTransformFeedback"><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" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glBeginTransformFeedback</b>(</code></td><td>GLenum <var class="pdparam">primitiveMode</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><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="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glEndTransformFeedback</b>(</code></td><td><var class="pdparam">void</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Description"><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 border="1"><colgroup><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>
+ Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
+ </strong></span></th><th align="left"><span class="bold"><strong>
+ Allowed Render Primitive <em class="parameter"><code>modes</code></em>
+ </strong></span></th></tr></thead><tbody><tr><td align="left">
+ <code class="constant">GL_POINTS</code>
+ </td><td align="left">
+ <code class="constant">GL_POINTS</code>
+ </td></tr><tr><td align="left">
+ <code class="constant">GL_LINES</code>
+ </td><td 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 align="left">
+ <code class="constant">GL_TRIANGLES</code>
+ </td><td 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 border="1"><colgroup><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>
+ Transform Feedback <em class="parameter"><code>primitiveMode</code></em>
+ </strong></span></th><th align="left"><span class="bold"><strong>
+ Allowed Geometry Shader Output Primitive Type
+ </strong></span></th></tr></thead><tbody><tr><td align="left">
+ <code class="constant">GL_POINTS</code>
+ </td><td align="left">
+ <code class="constant">points</code>
+ </td></tr><tr><td align="left">
+ <code class="constant">GL_LINES</code>
+ </td><td align="left">
+ <code class="constant">line_strip</code>
+ </td></tr><tr><td align="left">
+ <code class="constant">GL_TRIANGLES</code>
+ </td><td align="left">
+ <code class="constant">triangle_strip</code>
+ </td></tr></tbody></table></div><p>
+ </p></div><div class="refsect1" title="Notes"><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" title="Errors"><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" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
+ Copyright <span class="trademark"></span>© 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.
+ <a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
+ </p></div></div></body></html>