upstream-doc/man2/xhtml/glClear.xml

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   3 <?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>
   4                     Bitwise OR of masks that indicate the buffers to be cleared.
   5                     The four masks are
   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>.
  16         </p><p>
  17             The pixel ownership test,
  18             the scissor test,
  19             dithering, and the buffer writemasks affect the operation of <code class="function">glClear</code>.
  20             The scissor box bounds the cleared region.
  21             Alpha function,
  22             blend function,
  23             logical operation,
  24             stenciling,
  25             texture mapping,
  26             and depth-buffering are ignored by <code class="function">glClear</code>.
  27         </p><p>
  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.
  30         </p><p>
  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
  34                         writing.
  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>.
  50         </p><p>
  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>
  56         </p><p>
  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>
  58         </p><p>
  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>
  60         </p><p>
  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>
  62         </p><p>
  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>