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<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glDrawBuffers</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><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 border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><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.xml"><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.xml"><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.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
	and the corresponding execution of
	<a class="citerefentry" href="glEnd.xml"><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.xml"><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.xml"><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><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> <a class="citerefentry" href="glBlendFunc.xml"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,
	<a class="citerefentry" href="glColorMask.xml"><span class="citerefentry"><span class="refentrytitle">glColorMask</span></span></a>,
	<a class="citerefentry" href="glDrawBuffers.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffers</span></span></a>,
	<a class="citerefentry" href="glIndexMask.xml"><span class="citerefentry"><span class="refentrytitle">glIndexMask</span></span></a>,
	<a class="citerefentry" href="glLogicOp.xml"><span class="citerefentry"><span class="refentrytitle">glLogicOp</span></span></a>,
	<a class="citerefentry" href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a></p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 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="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
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