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glGetTransformFeedbackVarying.xhtml
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glGetTransformFeedbackVarying.xhtml
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<div class="refentry" id="glGetTransformFeedbackVarying">
<div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>glGetTransformFeedbackVarying — retrieve information about varying variables selected for transform feedback</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">glGetTransformFeedbackVarying</strong>(</code>
</td>
<td>GLuint<var class="pdparam">program</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLuint<var class="pdparam">index</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLsizei<var class="pdparam">bufSize</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLsizei *<var class="pdparam">length</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLsizei *<var class="pdparam">size</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLenum *<var class="pdparam">type</var>, </td>
</tr>
<tr>
<td> </td>
<td>char *<var class="pdparam">name</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>program</code>
</em>
</span>
</dt>
<dd>
<p>
The name of the target program object.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>index</code>
</em>
</span>
</dt>
<dd>
<p>
The index of the varying variable whose information to retrieve.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>bufSize</code>
</em>
</span>
</dt>
<dd>
<p>
The maximum number of characters, including the null terminator, that may be written into <em class="parameter"><code>name</code></em>.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>length</code>
</em>
</span>
</dt>
<dd>
<p>
The address of a variable which will receive the number of characters written into <em class="parameter"><code>name</code></em>,
excluding the null-terminator. If <em class="parameter"><code>length</code></em> is <code class="constant">NULL</code> no length is returned.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>size</code>
</em>
</span>
</dt>
<dd>
<p>
The address of a variable that will receive the size of the varying.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>type</code>
</em>
</span>
</dt>
<dd>
<p>
The address of a variable that will recieve the type of the varying.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>name</code>
</em>
</span>
</dt>
<dd>
<p>
The address of a buffer into which will be written the name of the varying.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
Information about the set of varying variables in a linked program that will be captured
during transform feedback may be retrieved by calling <code class="function">glGetTransformFeedbackVarying</code>.
<code class="function">glGetTransformFeedbackVarying</code> provides information about the varying
variable selected by <em class="parameter"><code>index</code></em>. An <em class="parameter"><code>index</code></em> of 0 selects
the first varying variable specified in the <em class="parameter"><code>varyings</code></em> array passed
to <a class="citerefentry" href="glTransformFeedbackVaryings"><span class="citerefentry"><span class="refentrytitle">glTransformFeedbackVaryings</span></span></a>, and
an <em class="parameter"><code>index</code></em> of the value of
<code class="constant">GL_TRANSFORM_FEEDBACK_VARYINGS</code> minus one selects
the last such variable.
</p>
<p>
The name of the selected varying is returned as a null-terminated string in
<em class="parameter"><code>name</code></em>. The actual number of characters written into <em class="parameter"><code>name</code></em>,
excluding the null terminator, is returned in <em class="parameter"><code>length</code></em>. If <em class="parameter"><code>length</code></em>
is NULL, no length is returned. The maximum number of characters that may be written into <em class="parameter"><code>name</code></em>,
including the null terminator, is specified by <em class="parameter"><code>bufSize</code></em>.
</p>
<p>
The length of the longest varying name in program is given by <code class="constant">GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH</code>,
which can be queried with <a class="citerefentry" href="glGetProgram"><span class="citerefentry"><span class="refentrytitle">glGetProgram</span></span></a>.
</p>
<p>
For the selected varying variable, its type is returned into <em class="parameter"><code>type</code></em>. The size of
the varying is returned into <em class="parameter"><code>size</code></em>. The value in <em class="parameter"><code>size</code></em> is
in units of the type returned in <em class="parameter"><code>type</code></em>. The type returned can be any of the
scalar, vector, or matrix attribute types returned by <a class="citerefentry" href="glGetActiveAttrib"><span class="citerefentry"><span class="refentrytitle">glGetActiveAttrib</span></span></a>.
If an error occurred, the return parameters <em class="parameter"><code>length</code></em>, <em class="parameter"><code>size</code></em>,
<em class="parameter"><code>type</code></em> and <em class="parameter"><code>name</code></em> will be unmodified. This command will return as much
information about the varying variables as possible. If no information is available, <em class="parameter"><code>length</code></em>
will be set to zero and <em class="parameter"><code>name</code></em> will be an empty string. This situation could
arise if <code class="function">glGetTransformFeedbackVarying</code> is called after a failed link.
</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p>
<code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>program</code></em> is not
the name of a program object.
</p>
<p>
<code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>index</code></em> is greater or equal to
the value of <code class="constant">GL_TRANSFORM_FEEDBACK_VARYINGS</code>.
</p>
<p>
<code class="constant">GL_INVALID_OPERATION</code> is generated <em class="parameter"><code>program</code></em> has not been linked.
</p>
</div>
<div class="refsect1" id="associatedgets">
<h2>Associated Gets</h2>
<p>
<a class="citerefentry" href="glGetProgram"><span class="citerefentry"><span class="refentrytitle">glGetProgram</span></span></a> with argument <code class="constant">GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH</code>.
</p>
</div>
{$pipelinestall}{$examples}
<div class="refsect1" id="versions">
<h2>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; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<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 Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature 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>2.1</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-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glGetTransformFeedbackVarying</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; 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="glBeginTransformFeedback"><span class="citerefentry"><span class="refentrytitle">glBeginTransformFeedback</span></span></a>,
<a class="citerefentry" href="glEndTransformFeedback"><span class="citerefentry"><span class="refentrytitle">glEndTransformFeedback</span></span></a>,
<a class="citerefentry" href="glTransformFeedbackVaryings"><span class="citerefentry"><span class="refentrytitle">glTransformFeedbackVaryings</span></span></a>,
<a class="citerefentry" href="glGetProgram"><span class="citerefentry"><span class="refentrytitle">glGetProgram</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="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p>
</div>
</div>