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renderer=
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"text/html; charset=UTF-8" /><link rel=
"stylesheet" type=
"text/css" href=
"opengl-man.css" /><title>glDrawBuffers
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.69.1" /></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
5 <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
6 specifying the buffers into which fragment colors or
7 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
8 buffers into which outputs from the fragment shader data will
9 be written. If a fragment shader writes a value
10 to one or more user defined output
11 variables, then the value of each variable will be written into the
12 buffer specified at a location within
<em class=
"parameter"><code>bufs
</code></em>
13 corresponding to the location assigned to that user defined output.
14 The draw buffer used for user defined outputs assigned to locations
15 greater than or equal to
<em class=
"parameter"><code>n
</code></em> is implicitly set
16 to
<code class=
"constant">GL_NONE
</code> and any data written to such an output
17 is discarded.
</p><p>The symbolic constants contained in
18 <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
19 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
20 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
21 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
22 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
23 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
24 <span class=
"emphasis"><em>n
</em></span>th color attachment of the current framebuffer.
25 <span class=
"emphasis"><em>n
</em></span> may range from
0 to the value of
26 <code class=
"constant">GL_MAX_COLOR_ATTACHMENTS
</code>.
</p></dd></dl></div><p>Except for
<code class=
"constant">GL_NONE
</code>, the preceding
27 symbolic constants may not appear more than once in
28 <em class=
"parameter"><code>bufs
</code></em>. The maximum number of draw buffers
29 supported is implementation dependent and can be queried by
31 <a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a>
32 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>,
33 <code class=
"constant">GL_BACK
</code>,
<code class=
"constant">GL_LEFT
</code>,
34 <code class=
"constant">GL_RIGHT
</code>, and
35 <code class=
"constant">GL_FRONT_AND_BACK
</code> are not allowed in the
36 <em class=
"parameter"><code>bufs
</code></em> array since they may refer to
37 multiple buffers.
</p><p>If a fragment shader does not write to a user defined output variable,
38 the values of the fragment
39 colors following shader execution are undefined. For each
40 fragment generated in this situation, a different value may be
41 written into each of the buffers specified by
42 <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
43 values in
<em class=
"parameter"><code>bufs
</code></em> is not an accepted
44 value.
</p><p><code class=
"constant">GL_INVALID_ENUM
</code> is generated if the GL is bound
45 to the default framebuffer and one or more of the values in
46 <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>
47 tokens.
</p><p><code class=
"constant">GL_INVALID_ENUM
</code> is generated if the GL is bound
48 to a framebuffer object and one or more of the values in
<em class=
"parameter"><code>bufs
</code></em>
49 is anything other than
<code class=
"constant">GL_NONE
</code> or one of the
50 <code class=
"constant">GL_COLOR_ATTACHMENTS
<span class=
"emphasis"><em>n
</em></span></code> tokens.
</p><p><code class=
"constant">GL_INVALID_ENUM
</code> is generated if
51 <em class=
"parameter"><code>n
</code></em> is less than
0.
</p><p><code class=
"constant">GL_INVALID_OPERATION
</code> is generated if a
52 symbolic constant other than
<code class=
"constant">GL_NONE
</code>
53 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
54 the entries in
<em class=
"parameter"><code>bufs
</code></em> (other than
55 <code class=
"constant">GL_NONE
</code> ) indicates a color buffer that
56 does not exist in the current GL context.
</p><p><code class=
"constant">GL_INVALID_VALUE
</code> is generated if
57 <em class=
"parameter"><code>n
</code></em> is greater than
58 <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.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a>
59 with argument
<code class=
"constant">GL_MAX_DRAW_BUFFERS
</code></p><p><a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a>
60 with argument
<code class=
"constant">GL_DRAW_BUFFER
<span class=
"emphasis"><em>i
</em></span></code> where
61 <code class=
"code"><span class=
"emphasis"><em>i
</em></span></code> indicates the number of the draw buffer
62 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 href=
"glBlendFunc.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBlendFunc
</span></span></a>,
63 <a href=
"glColorMask.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glColorMask
</span></span></a>,
64 <a href=
"glDrawBuffers.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawBuffers
</span></span></a>,
65 <a href=
"glLogicOp.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glLogicOp
</span></span></a>,
66 <a 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>
67 Copyright
<span class=
"trademark"></span>©
2003-
2005 3Dlabs Inc. Ltd.
68 This material may be distributed subject to the terms and conditions set forth in
69 the Open Publication License, v
1.0,
8 June
1999.
70 <a href=
"http://opencontent.org/openpub/" target=
"_top">http://opencontent.org/openpub/
</a>.
71 </p></div></div></body></html>
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