1 <!DOCTYPE html PUBLIC
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3 <?xml-stylesheet type=
"text/xsl" href=
"mathml.xsl"?><html xmlns=
"http://www.w3.org/1999/xhtml" xmlns:
pref=
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renderer=
"mathplayer-dl"><head><meta http-equiv=
"Content-Type" content=
"text/html; charset=UTF-8" /><title>glClear
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.73.2" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"glClear"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>glClear — clear buffers to preset values
</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">glClear
</b>(
</code></td><td>GLbitfield
</td><td><var class=
"pdparam">mask
</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>mask
</code></em></span></dt><dd><p>
4 Bitwise OR of masks that indicate the buffers to be cleared.
6 <code class=
"constant">GL_COLOR_BUFFER_BIT
</code>,
7 <code class=
"constant">GL_DEPTH_BUFFER_BIT
</code>,
8 <code class=
"constant">GL_ACCUM_BUFFER_BIT
</code>, and
9 <code class=
"constant">GL_STENCIL_BUFFER_BIT
</code>.
10 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
11 <code class=
"function">glClear
</code> sets the bitplane area of the window to values previously selected
12 by
<code class=
"function">glClearColor
</code>,
<code class=
"function">glClearIndex
</code>,
<code class=
"function">glClearDepth
</code>,
13 <code class=
"function">glClearStencil
</code>, and
<code class=
"function">glClearAccum
</code>.
14 Multiple color buffers can be cleared simultaneously by selecting
15 more than one buffer at a time using
<a class=
"citerefentry" href=
"glDrawBuffer.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawBuffer
</span></span></a>.
17 The pixel ownership test,
19 dithering, and the buffer writemasks affect the operation of
<code class=
"function">glClear
</code>.
20 The scissor box bounds the cleared region.
26 and depth-buffering are ignored by
<code class=
"function">glClear
</code>.
28 <code class=
"function">glClear
</code> takes a single argument that is the bitwise OR of several
29 values indicating which buffer is to be cleared.
31 The values are as follows:
32 </p><div class=
"variablelist"><dl><dt><span class=
"term"><code class=
"constant">GL_COLOR_BUFFER_BIT
</code></span></dt><dd><p>
33 Indicates the buffers currently enabled for color
35 </p></dd><dt><span class=
"term"><code class=
"constant">GL_DEPTH_BUFFER_BIT
</code></span></dt><dd><p>
36 Indicates the depth buffer.
37 </p></dd><dt><span class=
"term"><code class=
"constant">GL_ACCUM_BUFFER_BIT
</code></span></dt><dd><p>
38 Indicates the accumulation buffer.
39 </p></dd><dt><span class=
"term"><code class=
"constant">GL_STENCIL_BUFFER_BIT
</code></span></dt><dd><p>
40 Indicates the stencil buffer.
41 </p></dd></dl></div><p>
42 The value to which each buffer is cleared depends on the setting of the
43 clear value for that buffer.
44 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"notes"></a><h2>Notes
</h2><p>
45 If a buffer is not present,
46 then a
<code class=
"function">glClear
</code> directed at that buffer has no effect.
47 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"errors"></a><h2>Errors
</h2><p>
48 <code class=
"constant">GL_INVALID_VALUE
</code> is generated if any bit other than the four defined
49 bits is set in
<em class=
"parameter"><code>mask
</code></em>.
51 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated if
<code class=
"function">glClear
</code>
52 is executed between the execution of
<a class=
"citerefentry" href=
"glBegin.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glBegin
</span></span></a>
53 and the corresponding execution of
<a class=
"citerefentry" href=
"glEnd.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glEnd
</span></span></a>.
54 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"associatedgets"></a><h2>Associated Gets
</h2><p>
55 <a class=
"citerefentry" href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_ACCUM_CLEAR_VALUE
</code>
57 <a class=
"citerefentry" href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_DEPTH_CLEAR_VALUE
</code>
59 <a class=
"citerefentry" href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_INDEX_CLEAR_VALUE
</code>
61 <a class=
"citerefentry" href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_COLOR_CLEAR_VALUE
</code>
63 <a class=
"citerefentry" href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_STENCIL_CLEAR_VALUE
</code>
64 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"seealso"></a><h2>See Also
</h2><p>
65 <code class=
"function">glClearAccum
</code>,
66 <code class=
"function">glClearColor
</code>,
67 <code class=
"function">glClearDepth
</code>,
68 <code class=
"function">glClearIndex
</code>,
69 <code class=
"function">glClearStencil
</code>,
70 <a class=
"citerefentry" href=
"glColorMask.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glColorMask
</span></span></a>,
71 <a class=
"citerefentry" href=
"glDepthMask.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDepthMask
</span></span></a>,
72 <a class=
"citerefentry" href=
"glDrawBuffer.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawBuffer
</span></span></a>,
73 <a class=
"citerefentry" href=
"glScissor.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glScissor
</span></span></a>,
74 <a class=
"citerefentry" href=
"glStencilMask.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glStencilMask
</span></span></a>
75 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
76 Copyright
<span class=
"trademark"></span>©
1991-
2006
77 Silicon Graphics, Inc. This document is licensed under the SGI
78 Free Software B License. For details, see
79 <a class=
"ulink" href=
"http://oss.sgi.com/projects/FreeB/" target=
"_top">http://oss.sgi.com/projects/FreeB/
</a>.
80 </p></div></div></body></html>