<div class="refentry" id="glDrawBuffers">

<div class="titlepage"></div>

<div class="refnamediv">

<h2>Name</h2>

<p>glDrawBuffers — Specifies a list of color buffers to be drawn into</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">glDrawBuffers</strong>(</code>

</td>

<td>GLsizei <var class="pdparam">n</var>, </td>

</tr>

<tr>

<td> </td>

<td>const GLenum *<var class="pdparam">bufs</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>n</code>

</em>

</span>

</dt>

<dd>

<p>Specifies the number of buffers in

<em class="parameter"><code>bufs</code></em>.</p>

</dd>

<dt>

<span class="term">

<em class="parameter">

<code>bufs</code>

</em>

</span>

</dt>

<dd>

<p>Points to an array of symbolic constants

specifying the buffers into which fragment colors or

data values will be written.</p>

</dd>

</dl>

</div>

</div>

<div class="refsect1" id="description">

<h2>Description</h2>

<p><code class="function">glDrawBuffers</code> defines an array of

buffers into which outputs from the fragment shader data will

be written. If a fragment shader writes a value

to one or more user defined output

variables, then the value of each variable will be written into the

buffer specified at a location within <em class="parameter"><code>bufs</code></em>

corresponding to the location assigned to that user defined output.

The draw buffer used for user defined outputs assigned to locations

greater than or equal to <em class="parameter"><code>n</code></em> is implicitly set

to <code class="constant">GL_NONE</code> and any data written to such an output

is discarded.</p>

<p>The symbolic constants contained in

<em class="parameter"><code>bufs</code></em> must be one of the following, depending on

whether GL is bound to the default framebuffer or not:</p>

<div class="variablelist">

<dl class="variablelist">

<dt>

<span class="term">

<code class="constant">GL_NONE</code>

</span>

</dt>

<dd>

<p>The fragment shader output value is not written into

any color buffer.</p>

</dd>

<dt>

<span class="term">

<code class="constant">GL_BACK</code>

</span>

</dt>

<dd>

<p>The fragment shader output value is written into the

back color buffer.</p>

</dd>

<dt>

<span class="term">

<code class="constant">GL_COLOR_ATTACHMENT</code>

<span class="emphasis">

<em>n</em>

</span>

</span>

</dt>

<dd>

<p>The fragment shader output value is written into the

<span class="emphasis"><em>n</em></span>th color attachment of the current framebuffer.

<span class="emphasis"><em>n</em></span> may range from zero to the value of

<code class="constant">GL_MAX_COLOR_ATTACHMENTS</code>.</p>

</dd>

</dl>

</div>

<p>Except for <code class="constant">GL_NONE</code>, the preceding

symbolic constants may not appear more than once in

<em class="parameter"><code>bufs</code></em>. The maximum number of draw buffers

supported is implementation dependent and can be queried by

calling

<a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>

with the argument <code class="constant">GL_MAX_DRAW_BUFFERS</code>.</p>

</div>

<div class="refsect1" id="notes">

<h2>Notes</h2>

<p>If a fragment shader does not write to a user defined output variable,

the values of the fragment

colors following shader execution are undefined. For each

fragment generated in this situation, a different value may be

written into each of the buffers specified by

<em class="parameter"><code>bufs</code></em>.</p>

</div>

<div class="refsect1" id="errors">

<h2>Errors</h2>

<p><code class="constant">GL_INVALID_ENUM</code> is generated if one of the

values in <em class="parameter"><code>bufs</code></em> is not an accepted

value.</p>

<p><code class="constant">GL_INVALID_OPERATION</code> is generated if the GL is bound

to the default framebuffer and <em class="parameter"><code>n</code></em> is not 1, or if the value in

<em class="parameter"><code>bufs</code></em> is one of the <code class="constant">GL_COLOR_ATTACHMENT</code><span class="emphasis"><em>n</em></span>

tokens.</p>

<p><code class="constant">GL_INVALID_OPERATION</code> is generated if the GL is bound

to a framebuffer object and the ith buffer listed in <em class="parameter"><code>bufs</code></em>

is anything other than <code class="constant">GL_NONE</code> or

<code class="constant">GL_COLOR_ATTACHMENTS</code><span class="emphasis"><em>i</em></span>.</p>

<p><code class="constant">GL_INVALID_VALUE</code> is generated if

<em class="parameter"><code>n</code></em> is less than 0 or greater than

<code class="constant">GL_MAX_DRAW_BUFFERS</code>.</p>

</div>

<div class="refsect1" id="associatedgets">

<h2>Associated Gets</h2>

<p><a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>

with argument <code class="constant">GL_MAX_DRAW_BUFFERS</code></p>

<p><a class="citerefentry" href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>

with argument <code class="constant">GL_DRAW_BUFFER</code><span class="emphasis"><em>i</em></span> where

<span class="emphasis"><em>i</em></span> indicates the number of the draw buffer

whose value is to be queried.</p>

</div>

{$pipelinestall}{$examples}

<div class="refsect1" id="versions">

<h2>API 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; " 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="3">

<span class="bold"><strong>OpenGL ES API 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>2.0</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-bottom: 2px solid ; ">

<span class="bold"><strong>3.1</strong></span>

</th>

</tr>

</thead>

<tbody>

<tr>

<td style="text-align: left; border-right: 2px solid ; ">glDrawBuffers</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="glReadBuffer"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>

</p>

</div>

<div class="refsect1" id="Copyright">

<h2>Copyright</h2>

<p>

Copyright © 2003-2005 3Dlabs Inc. Ltd.

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="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p>

</div>

</div>