<div class="refentry" lang="en" xml:lang="en"><a id="glDrawBuffers"></a><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><tr><td><code class="funcdef">void <b class="fsfunc">glDrawBuffers</b>(</code></td><td>GLsizei  </td><td><var class="pdparam">n</var>, </td></tr><tr><td> </td><td>const GLenum * </td><td><var class="pdparam">bufs</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><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" lang="en" xml:lang="en"><a id="description"></a><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> may be any of the following:</p><div class="variablelist"><dl><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_FRONT_LEFT</code></span></dt><dd><p>The fragment shader output value is written into the

front left color buffer.</p></dd><dt><span class="term"><code class="constant">GL_FRONT_RIGHT</code></span></dt><dd><p>The fragment shader output value is written into the

front right color buffer.</p></dd><dt><span class="term"><code class="constant">GL_BACK_LEFT</code></span></dt><dd><p>The fragment shader output value is written into the

back left color buffer.</p></dd><dt><span class="term"><code class="constant">GL_BACK_RIGHT</code></span></dt><dd><p>The fragment shader output value is written into the

back right color buffer.</p></dd><dt><span class="term"><code class="constant">GL_COLOR_ATTACHMENT<span class="emphasis"><em>n</em></span></code></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 0 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 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" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>The symbolic constants <code class="constant">GL_FRONT</code>,

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

<code class="constant">GL_RIGHT</code>, and

<code class="constant">GL_FRONT_AND_BACK</code> are not allowed in the

<em class="parameter"><code>bufs</code></em> array since they may refer to

multiple buffers.</p><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" lang="en" xml:lang="en"><a id="errors"></a><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_ENUM</code> is generated if the GL is bound

to the default framebuffer and one or more of the values in

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

tokens.</p><p><code class="constant">GL_INVALID_ENUM</code> is generated if the GL is bound

to a framebuffer object and one or more of the values in <em class="parameter"><code>bufs</code></em>

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

<code class="constant">GL_COLOR_ATTACHMENT<span class="emphasis"><em>n</em></span></code> tokens.</p><p><code class="constant">GL_INVALID_ENUM</code> is generated if

<em class="parameter"><code>n</code></em> is less than 0.</p><p><code class="constant">GL_INVALID_OPERATION</code> is generated if a

symbolic constant other than <code class="constant">GL_NONE</code>

appears more than once in <em class="parameter"><code>bufs</code></em>.</p><p><code class="constant">GL_INVALID_OPERATION</code> is generated if any of

the entries in <em class="parameter"><code>bufs</code></em> (other than

<code class="constant">GL_NONE</code> ) indicates a color buffer that

does not exist in the current GL context.</p><p><code class="constant">GL_INVALID_VALUE</code> is generated if

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

<code class="constant">GL_MAX_DRAW_BUFFERS</code>.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p><a 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 href="glGet"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>

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

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

whose value is to be queried</p></div>

{$pipelinestall}{$examples}

<div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> <a href="glBlendFunc"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,

<a href="glColorMask"><span class="citerefentry"><span class="refentrytitle">glColorMask</span></span></a>,

<a href="glDrawBuffers"><span class="citerefentry"><span class="refentrytitle">glDrawBuffers</span></span></a>,

<a href="glLogicOp"><span class="citerefentry"><span class="refentrytitle">glLogicOp</span></span></a>,

<a href="glReadBuffer"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a></p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>

Copyright © 2003-2005 3Dlabs Inc. Ltd.

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

</p></div></div></div>