upstream-man-pages/man2/xhtml/glBeginQuery.xml

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
   2 <!-- saved from url=(0013)about:internet -->
   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>glBeginQuery</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glBeginQuery"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glBeginQuery — delimit the boundaries of a query object</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">glBeginQuery</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLuint  </td><td><var class="pdparam">id</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>target</code></em></span></dt><dd><p>
   4                     Specifies the target type of query object established between
   5                     <code class="function">glBeginQuery</code> and the subsequent <a class="citerefentry" href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>.
   6                     The symbolic constant must be <code class="constant">GL_SAMPLES_PASSED</code>.
   7                 </p></dd><dt><span class="term"><em class="parameter"><code>id</code></em></span></dt><dd><p>
   8                     Specifies the name of a query object.
   9                 </p></dd></dl></div></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">glEndQuery</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>target</code></em></span></dt><dd><p>
  10                     Specifies the target type of query object to be concluded.
  11                     The symbolic constant must be <code class="constant">GL_SAMPLES_PASSED</code>.
  12                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  13             <code class="function">glBeginQuery</code> and <a class="citerefentry" href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a> delimit the
  14             boundaries of a query object.  If a query object with name <em class="parameter"><code>id</code></em> does not yet exist it is created.
  15         </p><p>
  16             When <code class="function">glBeginQuery</code> is executed, the query object's samples-passed counter is reset to 0.  Subsequent
  17             rendering will increment the counter once for every sample that passes the depth test.  When <code class="function">glEndQuery</code>
  18             is executed, the samples-passed counter is assigned to the query object's result value.  This value can be queried by
  19             calling <a class="citerefentry" href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
  20             <code class="constant">GL_QUERY_RESULT</code>.
  21         </p><p>
  22             Querying the <code class="constant">GL_QUERY_RESULT</code> implicitly flushes the GL pipeline until the rendering delimited by the
  23             query object has completed and the result is available.  <code class="constant">GL_QUERY_RESULT_AVAILABLE</code> can be queried to
  24             determine if the result is immediately available or if the rendering is not yet complete.
  25         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
  26             If the samples-passed count exceeds the maximum value representable in the number of available bits, as reported by
  27             <a class="citerefentry" href="glGetQueryiv.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryiv</span></span></a> with <em class="parameter"><code>pname</code></em>
  28             <code class="constant">GL_QUERY_COUNTER_BITS</code>, the count becomes undefined.
  29         </p><p>
  30             An implementation may support 0 bits in its samples-passed counter, in which case query results are always undefined
  31             and essentially useless.
  32         </p><p>
  33             When <code class="constant">GL_SAMPLE_BUFFERS</code> is 0, the samples-passed counter will increment once for each fragment that passes
  34             the depth test.  When <code class="constant">GL_SAMPLE_BUFFERS</code> is 1, an implementation may either increment the samples-passed
  35             counter individually for each sample of a fragment that passes the depth test, or it may choose to increment the counter for
  36             all samples of a fragment if any one of them passes the depth test.
  37         </p><p>
  38             <code class="function">glBeginQuery</code> and <a class="citerefentry" href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>
  39             are available only if the GL version is 1.5 or greater.
  40         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
  41             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> is not <code class="constant">GL_SAMPLES_PASSED</code>.
  42         </p><p>
  43             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginQuery</code> is executed while
  44             a query object of the same <em class="parameter"><code>target</code></em> is already active.
  45         </p><p>
  46             <code class="constant">GL_INVALID_OPERATION</code> is generated if <a class="citerefentry" href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>
  47             is executed when a query object of the same <em class="parameter"><code>target</code></em> is not active.
  48         </p><p>
  49             <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>id</code></em> is 0.
  50         </p><p>
  51             <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>id</code></em> is the name of an already active query object.
  52         </p><p>
  53             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginQuery</code> or
  54             <a class="citerefentry" href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a> is executed between the execution of
  55             <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> and the corresponding execution of
  56             <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
  57         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
  58             <a class="citerefentry" href="glDeleteQueries.xml"><span class="citerefentry"><span class="refentrytitle">glDeleteQueries</span></span></a>,
  59             <a class="citerefentry" href="glGenQueries.xml"><span class="citerefentry"><span class="refentrytitle">glGenQueries</span></span></a>,
  60             <a class="citerefentry" href="glGetQueryiv.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryiv</span></span></a>,
  61             <a class="citerefentry" href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a>,
  62             <a class="citerefentry" href="glIsQuery.xml"><span class="citerefentry"><span class="refentrytitle">glIsQuery</span></span></a>
  63         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
  64             Copyright <span class="trademark"></span>© 2005 Addison-Wesley.
  65             This material may be distributed subject to the terms and conditions set forth in
  66             the Open Publication License, v 1.0, 8 June 1999.
  67             <a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
  68         </p></div></div></body></html>