<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 fragment color values or fragment data will

be written. If no fragment shader is active, rendering

operations will generate only one fragment color per fragment

and it will be written into each of the buffers specified by

<em class="parameter"><code>bufs</code></em>. If a fragment shader is active and

it writes a value to the output variable

<code class="code">gl_FragColor</code>, then that value will be

written into each of the buffers specified by

<em class="parameter"><code>bufs</code></em>. If a fragment shader is active and

it writes a value to one or more elements of the output array

variable <code class="code">gl_FragData[]</code>, then the value of

<code class="code">gl_FragData[0] </code> will be written into the

first buffer specified by <em class="parameter"><code>bufs</code></em>, the value

of <code class="code">gl_FragData[1] </code> will be written into the

second buffer specified by <em class="parameter"><code>bufs</code></em>, and so

on up to <code class="code">gl_FragData[n-1]</code>. The draw buffer

used for <code class="code">gl_FragData[n]</code> and beyond is

implicitly set to be <code class="constant">GL_NONE</code>.</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 color/data 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 color/data 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 color/data 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 color/data 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 color/data value is written into the

back right color buffer.</p></dd><dt><span class="term"><code class="constant">GL_AUXi</code></span></dt><dd><p>The fragment color/data value is written into

auxiliary buffer <code class="code">i</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>. The

number of auxiliary buffers 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_AUX_BUFFERS</code>.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p><code class="function">glDrawBuffers</code> is available only if

the GL version is 2.0 or greater.</p><p>It is always the case that <code class="constant">GL_AUXi</code> =

<code class="constant">GL_AUX0</code> + <code class="code">i</code>.</p><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 writes to neither

<code class="code">gl_FragColor</code> nor

<code class="code">gl_FragData</code>, 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

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

<code class="function">glDrawBuffers</code> is executed between the

execution of

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

and the corresponding execution of

<a class="citerefentry" href="glEnd"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><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_BUFFERSi</code> where

<code class="code">i</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 class="citerefentry" href="glBlendFunc"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,

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

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

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

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

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

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