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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>glClear - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="glClear">
<div class="titlepage"/>
<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 style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">void <strong class="fsfunc">glClear</strong>(</code>
</td>
<td>GLbitfield <var class="pdparam">mask</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsect1" id="parameters">
<h2>Parameters</h2>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="parameter">
<code>mask</code>
</em>
</span>
</dt>
<dd>
<p>
Bitwise OR of masks that indicate the buffers to be cleared.
The three masks are
<code class="constant">GL_COLOR_BUFFER_BIT</code>,
<code class="constant">GL_DEPTH_BUFFER_BIT</code>, and
<code class="constant">GL_STENCIL_BUFFER_BIT</code>.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">glClear</code> sets the bitplane area of the window to values previously selected
by <code class="function">glClearColor</code>, <code class="function">glClearDepth</code>, and
<code class="function">glClearStencil</code>.
Multiple color buffers can be cleared simultaneously by selecting
more than one buffer at a time using <a class="citerefentry" href="glDrawBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>.
</p>
<p>
The pixel ownership test,
the scissor test,
dithering, and the buffer writemasks affect the operation of <code class="function">glClear</code>.
The scissor box bounds the cleared region.
Alpha function,
blend function,
logical operation,
stenciling,
texture mapping,
and depth-buffering are ignored by <code class="function">glClear</code>.
</p>
<p>
<code class="function">glClear</code> takes a single argument that is the bitwise OR of several
values indicating which buffer is to be cleared.
</p>
<p>
The values are as follows:
</p>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<code class="constant">GL_COLOR_BUFFER_BIT</code>
</span>
</dt>
<dd>
<p>
Indicates the buffers currently enabled for color
writing.
</p>
</dd>
<dt>
<span class="term">
<code class="constant">GL_DEPTH_BUFFER_BIT</code>
</span>
</dt>
<dd>
<p>
Indicates the depth buffer.
</p>
</dd>
<dt>
<span class="term">
<code class="constant">GL_STENCIL_BUFFER_BIT</code>
</span>
</dt>
<dd>
<p>
Indicates the stencil buffer.
</p>
</dd>
</dl>
</div>
<p>
The value to which each buffer is cleared depends on the setting of the
clear value for that buffer.
</p>
</div>
<div class="refsect1" id="notes">
<h2>Notes</h2>
<p>
If a buffer is not present,
then a <code class="function">glClear</code> directed at that buffer has no effect.
</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p>
<code class="constant">GL_INVALID_VALUE</code> is generated if any bit other than the three defined
bits is set in <em class="parameter"><code>mask</code></em>.
</p>
</div>
<div class="refsect1" id="associatedgets">
<h2>Associated Gets</h2>
<p>
<a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_DEPTH_CLEAR_VALUE</code>
</p>
<p>
<a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_COLOR_CLEAR_VALUE</code>
</p>
<p>
<a class="citerefentry" href="glGet.xhtml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_STENCIL_CLEAR_VALUE</code>
</p>
</div>
<div class="refsect1" id="versions">
<h2>Version Support</h2>
<div class="informaltable">
<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
<colgroup>
<col style="text-align: left; "/>
<col style="text-align: center; " class="firstvers"/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; " class="lastvers"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; ">
</th>
<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
<span class="bold"><strong>OpenGL Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glClear</code>
</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; border-right: 2px solid ; ">✔</td>
<td style="text-align: center; ">✔</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1" id="seealso">
<h2>See Also</h2>
<p>
<code class="function">glClearColor</code>,
<code class="function">glClearDepth</code>,
<code class="function">glClearStencil</code>,
<a class="citerefentry" href="glColorMask.xhtml"><span class="citerefentry"><span class="refentrytitle">glColorMask</span></span></a>,
<a class="citerefentry" href="glDepthMask.xhtml"><span class="citerefentry"><span class="refentrytitle">glDepthMask</span></span></a>,
<a class="citerefentry" href="glDrawBuffer.xhtml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
<a class="citerefentry" href="glScissor.xhtml"><span class="citerefentry"><span class="refentrytitle">glScissor</span></span></a>,
<a class="citerefentry" href="glStencilMask.xhtml"><span class="citerefentry"><span class="refentrytitle">glStencilMask</span></span></a>
</p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 1991-2006 Silicon Graphics, Inc.
Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
This document is licensed under the SGI Free Software B License.
For details, see
<a class="link" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
</p>
</div>
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