upstream-doc/man2/glBeginQuery.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glBeginQuery">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2005</year>
   9                 <holder>Sams Publishing</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glBeginQuery</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glBeginQuery</refname>
  17         <refpurpose>delimit the boundaries of a query object</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glBeginQuery</function></funcdef>
  23                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  24                 <paramdef>GLuint <parameter>id</parameter></paramdef>
  25             </funcprototype>
  26         </funcsynopsis>
  27     </refsynopsisdiv>
  28     <!-- eqn: ignoring delim $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>target</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specifies the target type of query object established between
  36                     <function>glBeginQuery</function> and the subsequent <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>.
  37                     The symbolic constant must be <constant>GL_SAMPLES_PASSED</constant>.
  38                 </para>
  39             </listitem>
  40         </varlistentry>
  41         <varlistentry>
  42             <term><parameter>id</parameter></term>
  43             <listitem>
  44                 <para>
  45                     Specifies the name of a query object.
  46                 </para>
  47             </listitem>
  48         </varlistentry>
  49         </variablelist>
  50     </refsect1>
  51     <refsynopsisdiv><title>C Specification</title>
  52         <funcsynopsis>
  53             <funcprototype>
  54                 <funcdef>void <function>glEndQuery</function></funcdef>
  55                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  56             </funcprototype>
  57         </funcsynopsis>
  58     </refsynopsisdiv>
  59     <!-- eqn: ignoring delim $$ -->
  60     <refsect1 id="parameters2"><title>Parameters</title>
  61         <variablelist>
  62         <varlistentry>
  63             <term><parameter>target</parameter></term>
  64             <listitem>
  65                 <para>
  66                     Specifies the target type of query object to be concluded.
  67                     The symbolic constant must be <constant>GL_SAMPLES_PASSED</constant>.
  68                 </para>
  69             </listitem>
  70         </varlistentry>
  71         </variablelist>
  72     </refsect1>
  73     <refsect1 id="description"><title>Description</title>
  74         <para>
  75             <function>glBeginQuery</function> and <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry> delimit the
  76             boundaries of a query object.  If a query object with name <parameter>id</parameter> does not yet exist it is created.
  77         </para>
  78         <para>
  79             When <function>glBeginQuery</function> is executed, the query object's samples-passed counter is reset to 0.  Subsequent
  80             rendering will increment the counter once for every sample that passes the depth test.  When <function>glEndQuery</function>
  81             is executed, the samples-passed counter is assigned to the query object's result value.  This value can be queried by
  82             calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
  83             <constant>GL_QUERY_RESULT</constant>.
  84         </para>
  85         <para>
  86             Querying the <constant>GL_QUERY_RESULT</constant> implicitly flushes the GL pipeline until the rendering delimited by the
  87             query object has completed and the result is available.  <constant>GL_QUERY_RESULT_AVAILABLE</constant> can be queried to
  88             determine if the result is immediately available or if the rendering is not yet complete.
  89         </para>
  90     </refsect1>
  91     <refsect1 id="notes"><title>Notes</title>
  92         <para>
  93             If the samples-passed count exceeds the maximum value representable in the number of available bits, as reported by
  94             <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry> with <parameter>pname</parameter>
  95             <constant>GL_QUERY_COUNTER_BITS</constant>, the count becomes undefined.
  96         </para>
  97         <para>
  98             An implementation may support 0 bits in its samples-passed counter, in which case query results are always undefined
  99             and essentially useless.
 100         </para>
 101         <para>
 102             When <constant>GL_SAMPLE_BUFFERS</constant> is 0, the samples-passed counter will increment once for each fragment that passes
 103             the depth test.  When <constant>GL_SAMPLE_BUFFERS</constant> is 1, an implementation may either increment the samples-passed
 104             counter individually for each sample of a fragment that passes the depth test, or it may choose to increment the counter for
 105             all samples of a fragment if any one of them passes the depth test.
 106         </para>
 107         <para>
 108             <function>glBeginQuery</function> and <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>
 109             are available only if the GL version is 1.5 or greater.
 110         </para>
 111     </refsect1>
 112     <refsect1 id="errors"><title>Errors</title>
 113         <para>
 114             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not <constant>GL_SAMPLES_PASSED</constant>.
 115         </para>
 116         <para>
 117             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginQuery</function> is executed while
 118             a query object of the same <parameter>target</parameter> is already active.
 119         </para>
 120         <para>
 121             <constant>GL_INVALID_OPERATION</constant> is generated if <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>
 122             is executed when a query object of the same <parameter>target</parameter> is not active.
 123         </para>
 124         <para>
 125             <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is 0.
 126         </para>
 127         <para>
 128             <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is the name of an already active query object.
 129         </para>
 130         <para>
 131             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginQuery</function> or
 132             <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry> is executed between the execution of
 133             <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding execution of
 134             <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
 135         </para>
 136     </refsect1>
 137     <refsect1 id="seealso"><title>See Also</title>
 138         <para>
 139             <citerefentry><refentrytitle>glDeleteQueries</refentrytitle></citerefentry>,
 140             <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>,
 141             <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry>,
 142             <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry>,
 143             <citerefentry><refentrytitle>glIsQuery</refentrytitle></citerefentry>
 144         </para>
 145     </refsect1>
 146     <refsect1 id="Copyright"><title>Copyright</title>
 147         <para>
 148             Copyright <trademark class="copyright"></trademark> 2005 Addison-Wesley.
 149             This material may be distributed subject to the terms and conditions set forth in
 150             the Open Publication License, v 1.0, 8 June 1999.
 151             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 152         </para>
 153     </refsect1>
 154 </refentry>