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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>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>
                    Bitwise OR of masks that indicate the buffers to be cleared.
                    The four masks are
                    <code class="constant">GL_COLOR_BUFFER_BIT</code>,
                    <code class="constant">GL_DEPTH_BUFFER_BIT</code>,
                    <code class="constant">GL_ACCUM_BUFFER_BIT</code>, and
                    <code class="constant">GL_STENCIL_BUFFER_BIT</code>.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><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">glClearIndex</code>, <code class="function">glClearDepth</code>,
            <code class="function">glClearStencil</code>, and <code class="function">glClearAccum</code>.
            Multiple color buffers can be cleared simultaneously by selecting
            more than one buffer at a time using <a class="citerefentry" href="glDrawBuffer.xml"><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><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_ACCUM_BUFFER_BIT</code></span></dt><dd><p>
                        Indicates the accumulation 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" lang="en" xml:lang="en"><a id="notes"></a><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" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated if any bit other than the four defined
            bits is set in <em class="parameter"><code>mask</code></em>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glClear</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_ACCUM_CLEAR_VALUE</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_DEPTH_CLEAR_VALUE</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_INDEX_CLEAR_VALUE</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_COLOR_CLEAR_VALUE</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_STENCIL_CLEAR_VALUE</code>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <code class="function">glClearAccum</code>,
            <code class="function">glClearColor</code>,
            <code class="function">glClearDepth</code>,
            <code class="function">glClearIndex</code>,
            <code class="function">glClearStencil</code>,
            <a class="citerefentry" href="glColorMask.xml"><span class="citerefentry"><span class="refentrytitle">glColorMask</span></span></a>,
            <a class="citerefentry" href="glDepthMask.xml"><span class="citerefentry"><span class="refentrytitle">glDepthMask</span></span></a>,
            <a class="citerefentry" href="glDrawBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
            <a class="citerefentry" href="glScissor.xml"><span class="citerefentry"><span class="refentrytitle">glScissor</span></span></a>,
            <a class="citerefentry" href="glStencilMask.xml"><span class="citerefentry"><span class="refentrytitle">glStencilMask</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>© 1991-2006
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
