upstream-man-pages/man3/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 $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>target</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specifies the target type of query object established between
  36                     <function>glBeginQuery</function> and the subsequent <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>.
  37                     The symbolic constant must be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>,
  38                     <constant>GL_PRIMITIVES_GENERATED</constant>, <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or
  39                     <constant>GL_TIME_ELAPSED</constant>.
  40                 </para>
  41             </listitem>
  42         </varlistentry>
  43         <varlistentry>
  44             <term><parameter>id</parameter></term>
  45             <listitem>
  46                 <para>
  47                     Specifies the name of a query object.
  48                 </para>
  49             </listitem>
  50         </varlistentry>
  51         </variablelist>
  52     </refsect1>
  53     <refsynopsisdiv><title>C Specification</title>
  54         <funcsynopsis>
  55             <funcprototype>
  56                 <funcdef>void <function>glEndQuery</function></funcdef>
  57                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  58             </funcprototype>
  59         </funcsynopsis>
  60     </refsynopsisdiv>
  61     <!-- eqn: ignoring delim $$ -->
  62     <refsect1 id="parameters2"><title>Parameters</title>
  63         <variablelist>
  64         <varlistentry>
  65             <term><parameter>target</parameter></term>
  66             <listitem>
  67                 <para>
  68                     Specifies the target type of query object to be concluded.
  69                     The symbolic constant must be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>,
  70                     <constant>GL_PRIMITIVES_GENERATED</constant>, <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or
  71                     <constant>GL_TIME_ELAPSED</constant>.
  72                 </para>
  73             </listitem>
  74         </varlistentry>
  75         </variablelist>
  76     </refsect1>
  77     <refsect1 id="description"><title>Description</title>
  78         <para>
  79             <function>glBeginQuery</function> and <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry> delimit the
  80             boundaries of a query object.  <parameter>query</parameter> must be a name previously returned from a call to
  81             <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>. If a query object with name <parameter>id</parameter>
  82             does not yet exist it is created with the type determined by <parameter>target</parameter>. <parameter>target</parameter> must
  83             be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>, <constant>GL_PRIMITIVES_GENERATED</constant>,
  84             <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or <constant>GL_TIME_ELAPSED</constant>. The behavior of the query
  85             object depends on its type and is as follows.
  86         </para>
  87         <para>
  88             If <parameter>target</parameter> is <constant>GL_SAMPLES_PASSED</constant>, <parameter>id</parameter> must be an unused name,
  89             or the name of an existing occlusion query object.
  90             When <function>glBeginQuery</function> is executed, the query object's samples-passed counter is reset to 0.  Subsequent
  91             rendering will increment the counter for every sample that passes the depth test.  If the value of <constant>GL_SAMPLE_BUFFERS</constant>
  92             is 0, then the samples-passed count is incremented by 1 for each fragment. If the value of <constant>GL_SAMPLE_BUFFERS</constant>
  93             is 1, then the samples-passed count is incremented by the number of samples whose coverage bit is set. However, implementations, at their
  94             discression may instead increase the samples-passed count by the value of <constant>GL_SAMPLES</constant> if any sample in the fragment
  95             is covered. When <function>glEndQuery</function>
  96             is executed, the samples-passed counter is assigned to the query object's result value.  This value can be queried by
  97             calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
  98             <constant>GL_QUERY_RESULT</constant>.
  99         </para>
 100         <para>
 101             If <parameter>target</parameter> is <constant>GL_ANY_SAMPLES_PASSED</constant>, <parameter>id</parameter> must be an unused name,
 102             or the name of an existing boolean occlusion query object.
 103             When <function>glBeginQuery</function> is executed, the query object's samples-passed flag is reset to <constant>GL_FALSE</constant>.
 104             Subsequent rendering causes the flag to be set to <constant>GL_TRUE</constant> if any sample passes the depth test.  When
 105             <function>glEndQuery</function> is executed, the samples-passed flag is assigned to the query object's result value.  This value can
 106             be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
 107             <constant>GL_QUERY_RESULT</constant>.
 108         </para>
 109         <para>
 110             If <parameter>target</parameter> is <constant>GL_PRIMITIVES_GENERATED</constant>, <parameter>id</parameter> must be an unused
 111             name, or the name of an existing primitive query object previously bound to the <constant>GL_PRIMITIVES_GENERATED</constant> query binding.
 112             When <function>glBeginQuery</function> is executed, the query object's primitives-generated counter is reset to 0.  Subsequent
 113             rendering will increment the counter once for every vertex that is emitted from the geometry shader, or from the vertex shader if
 114             no geometry shader is present.  When <function>glEndQuery</function> is executed, the primitives-generated counter is assigned to
 115             the query object's result value.  This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
 116             <constant>GL_QUERY_RESULT</constant>.
 117         </para>
 118         <para>
 119             If <parameter>target</parameter> is <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, <parameter>id</parameter> must be
 120             an unused name, or the name of an existing primitive query object previously bound to the <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>
 121             query binding. When <function>glBeginQuery</function> is executed, the query object's primitives-written counter is reset to 0.  Subsequent
 122             rendering will increment the counter once for every vertex that is written into the bound transform feedback buffer(s).  If transform feedback
 123             mode is not activated between the call to <function>glBeginQuery</function> and <function>glEndQuery</function>, the counter will not be
 124             incremented.  When <function>glEndQuery</function> is executed, the primitives-written counter is assigned to
 125             the query object's result value.  This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
 126             <constant>GL_QUERY_RESULT</constant>.
 127         </para>
 128         <para>
 129             If <parameter>target</parameter> is <constant>GL_TIME_ELAPSED</constant>, <parameter>id</parameter> must be
 130             an unused name, or the name of an existing timer query object previously bound to the <constant>GL_TIME_ELAPSED</constant>
 131             query binding. When <function>glBeginQuery</function> is executed, the query object's time counter is reset to 0.  When <function>glEndQuery</function>
 132             is executed, the elapsed server time that has passed since the call to <function>glBeginQuery</function> is written into the query object's
 133             time counter.  This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter>
 134             <constant>GL_QUERY_RESULT</constant>.
 135         </para>
 136         <para>
 137             Querying the <constant>GL_QUERY_RESULT</constant> implicitly flushes the GL pipeline until the rendering delimited by the
 138             query object has completed and the result is available.  <constant>GL_QUERY_RESULT_AVAILABLE</constant> can be queried to
 139             determine if the result is immediately available or if the rendering is not yet complete.
 140         </para>
 141     </refsect1>
 142     <refsect1 id="notes"><title>Notes</title>
 143         <para>
 144             If the query target's count exceeds the maximum value representable in the number of available bits, as reported by
 145             <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry> with <parameter>target</parameter> set to the
 146             appropriate query target and <parameter>pname</parameter>
 147             <constant>GL_QUERY_COUNTER_BITS</constant>, the count becomes undefined.
 148         </para>
 149         <para>
 150             An implementation may support 0 bits in its counter, in which case query results are always undefined
 151             and essentially useless.
 152         </para>
 153         <para>
 154             When <constant>GL_SAMPLE_BUFFERS</constant> is 0, the samples-passed counter of an occlusion query will increment once for each
 155             fragment that passes the depth test.  When <constant>GL_SAMPLE_BUFFERS</constant> is 1, an implementation may either increment
 156             the samples-passed counter individually for each sample of a fragment that passes the depth test, or it may choose to increment
 157             the counter for all samples of a fragment if any one of them passes the depth test.
 158         </para>
 159         <para>
 160             The query targets <constant>GL_ANY_SAMPLES_PASSED</constant>, and <constant>GL_TIME_ELAPSED</constant> are availale only if
 161             the GL version is 3.3 or higher.
 162         </para>
 163     </refsect1>
 164     <refsect1 id="errors"><title>Errors</title>
 165         <para>
 166             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the accepted tokens.
 167         </para>
 168         <para>
 169             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginQuery</function> is executed while
 170             a query object of the same <parameter>target</parameter> is already active.
 171         </para>
 172         <para>
 173             <constant>GL_INVALID_OPERATION</constant> is generated if <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>
 174             is executed when a query object of the same <parameter>target</parameter> is not active.
 175         </para>
 176         <para>
 177             <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is 0.
 178         </para>
 179         <para>
 180             <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is the name of an already active query object.
 181         </para>
 182         <para>
 183             <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> refers to an existing query object whose type
 184             does not does not match <parameter>target</parameter>.
 185         </para>
 186     </refsect1>
 187     <refsect1 id="seealso"><title>See Also</title>
 188         <para>
 189             <citerefentry><refentrytitle>glDeleteQueries</refentrytitle></citerefentry>,
 190             <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>,
 191             <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry>,
 192             <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry>,
 193             <citerefentry><refentrytitle>glIsQuery</refentrytitle></citerefentry>
 194         </para>
 195     </refsect1>
 196     <refsect1 id="Copyright"><title>Copyright</title>
 197         <para>
 198             Copyright <trademark class="copyright"></trademark> 2005 Addison-Wesley.
 199             This material may be distributed subject to the terms and conditions set forth in
 200             the Open Publication License, v 1.0, 8 June 1999.
 201             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 202         </para>
 203     </refsect1>
 204 </refentry>