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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>glDrawArraysInstancedBaseInstance - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="glDrawArraysInstancedBaseInstance">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>glDrawArraysInstancedBaseInstance — draw multiple instances of a range of elements with offset applied to instanced attributes</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">glDrawArraysInstancedBaseInstance</strong>(</code>
</td>
<td>GLenum <var class="pdparam">mode</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLint <var class="pdparam">first</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLsizei <var class="pdparam">count</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLsizei <var class="pdparam">primcount</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLuint <var class="pdparam">baseinstance</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>mode</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies what kind of primitives to render. Symbolic constants <code class="constant">GL_POINTS</code>,
<code class="constant">GL_LINE_STRIP</code>, <code class="constant">GL_LINE_LOOP</code>, <code class="constant">GL_LINES</code>,
<code class="constant">GL_TRIANGLE_STRIP</code>, <code class="constant">GL_TRIANGLE_FAN</code>, <code class="constant">GL_TRIANGLES</code>
<code class="constant">GL_LINES_ADJACENCY</code>, <code class="constant">GL_LINE_STRIP_ADJACENCY</code>,
<code class="constant">GL_TRIANGLES_ADJACENCY</code>, <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code> and <code class="constant">GL_PATCHES</code>
are accepted.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>first</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the starting index in the enabled arrays.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>count</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the number of indices to be rendered.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>primcount</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the number of instances of the specified range of indices to be rendered.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>baseinstance</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the base instance for use in fetching instanced vertex attributes.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">glDrawArraysInstancedBaseInstance</code> behaves identically to <a class="citerefentry" href="glDrawArrays.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>
except that <em class="parameter"><code>primcount</code></em> instances of the range of elements are executed and the value of the internal counter
<em class="parameter"><code>instanceID</code></em> advances for each iteration. <em class="parameter"><code>instanceID</code></em> is an internal 32-bit integer counter
that may be read by a vertex shader as <code class="constant">gl_InstanceID</code>.
</p>
<p>
<code class="function">glDrawArraysInstancedBaseInstance</code> has the same effect as:
</p>
<pre class="programlisting"> if ( mode or count is invalid )
generate appropriate error
else {
for (int i = 0; i < primcount ; i++) {
instanceID = i;
glDrawArrays(mode, first, count);
}
instanceID = 0;
}</pre>
<p>
</p>
<p>
Specific vertex attributes may be classified as <span class="emphasis"><em>instanced</em></span> through the use of
<a class="citerefentry" href="glVertexAttribDivisor.xhtml"><span class="citerefentry"><span class="refentrytitle">glVertexAttribDivisor</span></span></a>. Instanced vertex attributes
supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex
attribute arrays is calculated as:
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mfenced open="⌊" close="⌋">
<mml:mfrac>
<mml:mrow>
<mml:mi>gl</mml:mi>
<mml:mo>_</mml:mo>
<mml:mi>InstanceID</mml:mi>
</mml:mrow>
<mml:mi>divisor</mml:mi>
</mml:mfrac>
</mml:mfenced>
<mml:mo lspace="2px" rspace="2px">+</mml:mo>
<mml:mi>baseInstance</mml:mi>
</mml:mrow>
</mml:math>. Note that <em class="parameter"><code>baseinstance</code></em>
does not affect the shader-visible value of
<code class="constant">gl_InstanceID</code>.
</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p>
<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not one of
the accepted values.
</p>
<p>
<code class="constant">GL_INVALID_OPERATION</code> is generated if a geometry shader is active and <em class="parameter"><code>mode</code></em>
is incompatible with the input primitive type of the geometry shader in the currently installed program object.
</p>
<p>
<code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>count</code></em> or <em class="parameter"><code>primcount</code></em> are negative.
</p>
<p>
<code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to an
enabled array and the buffer object's data store is currently mapped.
</p>
</div>
<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">glDrawArraysInstancedBaseInstance</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="glDrawArrays.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>,
<a class="citerefentry" href="glDrawElementsInstanced.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawElementsInstanced</span></span></a>
</p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 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="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p>
</div>
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