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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>gl_Layer - OpenGL 4 Reference Pages</title>
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<div class="refentry" id="gl_Layer">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>gl_Layer — contains the selected layer of a multi-layer framebuffer attachment</p>
</div>
<div class="refsynopsisdiv">
<h2>Declaration</h2>
<p>
</p>
<pre class="programlisting">// Geometry stage</pre>
<p>
<code class="fieldsynopsis"><span class="modifier">out </span><span class="type">int </span><span class="varname">gl_Layer </span>;</code>
</p>
<p>
</p>
<pre class="programlisting">// Fragment stage</pre>
<p>
<code class="fieldsynopsis"><span class="modifier">in </span><span class="type">int </span><span class="varname">gl_Layer </span>;</code>
</p>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
In the geometry language, <code class="varname">gl_Layer</code> is used to select a specific
layer (or face and layer of cube map) in a multi-layer framebuffer attachment. The actual
layer used will come from one of the vertices in the primitive being shaded. Which vertex
the layer comes from is undefined and as such it is recommended to write the same value
to <code class="varname">gl_Layer</code> for all vertices in the primitive. If a shader statically
assigns a value to <code class="varname">gl_Layer</code>, layered rendering mode is enabled.
If a shader statically assigns a value to <code class="varname">gl_Layer</code>, and there is an execution path through
the shader that does not set <code class="varname">gl_Layer</code>, then the value of <code class="varname">gl_Layer</code>
is undefined for invocations of the shader that take that path.
</p>
<p>
When used with an array of cube map textures, the <code class="varname">gl_Layer</code> output variable
takes on a special value. Instead of referring to only the layer, it is used to select a cube map
face and a layer. Setting <code class="varname">gl_Layer</code> to the value
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>layer</mml:mi><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mi>face</mml:mi></mml:math>
will render to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>face</mml:mi></mml:math>
of the cube defined in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>layer</mml:mi></mml:math>.
The face values are as follows:
</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 style="text-align: left; "/>
<col style="text-align: center; "/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong> Face Value </strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong> Resulting Target </strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
0
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
<code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_X</code>
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
1
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
<code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_X</code>
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
2
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
<code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_Y</code>
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
3
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
<code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_Y</code>
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
4
</td>
<td style="text-align: center; border-bottom: 2px solid ; ">
<code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_Z</code>
</td>
</tr>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
5
</td>
<td style="text-align: center; ">
<code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_Z</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
</p>
<p>
For example, to render to the positive y cube map face located in the 5<sup>th</sup> layer of the
cube map array, <code class="varname">gl_Layer</code> should be set to
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mn>5</mml:mn><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mn>2</mml:mn></mml:math>.
</p>
<p>
The input variable <code class="varname">gl_Layer</code> in the fragment language will have the same value that was written to the
output variable <code class="varname">gl_Layer</code> in the geometry language. If the geometry stage does not dynamically assign a
value to <code class="varname">gl_Layer</code>, the value of <code class="varname">gl_Layer</code> in the fragment stage will be undefined. If the geometry stage
makes no static assignment to <code class="varname">gl_Layer</code>, the input <code class="varname">gl_Layer</code> in the fragment stage will be zero. Otherwise,
the fragment stage will read the same value written by the geometry stage, even if that value is out of
range. If a fragment shader contains a static access to <code class="varname">gl_Layer</code>, it will count against the implementation
defined limit for the maximum number of inputs to the fragment stage.
</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 ; ">
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<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 Shading Language 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>1.10</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.20</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.40</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>1.50</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.00</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.10</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.20</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.30</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.40</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.50</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">gl_Layer (geometry stage)</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-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-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-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-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-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 ; ">gl_Layer (fragment stage)</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="gl_ViewportIndex.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_ViewportIndex</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>
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