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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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glBeginQuery - OpenGL 3.3 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></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"><p><code class="funcdef">void <b class="fsfunc">glBeginQuery</b>(</code>GLenum <var class="pdparam">target</var>, GLuint <var class="pdparam">id</var><code>)</code>;</p></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>
                    Specifies the target type of query object established between
                    <code class="function">glBeginQuery</code> and the subsequent <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>.
                    The symbolic constant must be one of <code class="constant">GL_SAMPLES_PASSED</code>, <code class="constant">GL_ANY_SAMPLES_PASSED</code>,
                    <code class="constant">GL_PRIMITIVES_GENERATED</code>, <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or
                    <code class="constant">GL_TIME_ELAPSED</code>.
                </p></dd><dt><span class="term"><em class="parameter"><code>id</code></em></span></dt><dd><p>
                    Specifies the name of a query object.
                </p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glEndQuery</b>(</code>GLenum <var class="pdparam">target</var><code>)</code>;</p></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>
                    Specifies the target type of query object to be concluded.
                    The symbolic constant must be one of <code class="constant">GL_SAMPLES_PASSED</code>, <code class="constant">GL_ANY_SAMPLES_PASSED</code>,
                    <code class="constant">GL_PRIMITIVES_GENERATED</code>, <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or
                    <code class="constant">GL_TIME_ELAPSED</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">glBeginQuery</code> and <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a> delimit the
            boundaries of a query object.  <em class="parameter"><code>query</code></em> must be a name previously returned from a call to
            <a href="glGenQueries.xml"><span class="citerefentry"><span class="refentrytitle">glGenQueries</span></span></a>. If a query object with name <em class="parameter"><code>id</code></em>
            does not yet exist it is created with the type determined by <em class="parameter"><code>target</code></em>. <em class="parameter"><code>target</code></em> must
            be one of <code class="constant">GL_SAMPLES_PASSED</code>, <code class="constant">GL_ANY_SAMPLES_PASSED</code>, <code class="constant">GL_PRIMITIVES_GENERATED</code>,
            <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or <code class="constant">GL_TIME_ELAPSED</code>. The behavior of the query
            object depends on its type and is as follows.
        </p><p>
            If <em class="parameter"><code>target</code></em> is <code class="constant">GL_SAMPLES_PASSED</code>, <em class="parameter"><code>id</code></em> must be an unused name,
            or the name of an existing occlusion query object.
            When <code class="function">glBeginQuery</code> is executed, the query object's samples-passed counter is reset to 0.  Subsequent
            rendering will increment the counter for every sample that passes the depth test.  If the value of <code class="constant">GL_SAMPLE_BUFFERS</code>
            is 0, then the samples-passed count is incremented by 1 for each fragment. If the value of <code class="constant">GL_SAMPLE_BUFFERS</code>
            is 1, then the samples-passed count is incremented by the number of samples whose coverage bit is set. However, implementations, at their
            discression may instead increase the samples-passed count by the value of <code class="constant">GL_SAMPLES</code> if any sample in the fragment
            is covered. When <code class="function">glEndQuery</code>
            is executed, the samples-passed counter is assigned to the query object's result value.  This value can be queried by
            calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_RESULT</code>.
        </p><p>
            If <em class="parameter"><code>target</code></em> is <code class="constant">GL_ANY_SAMPLES_PASSED</code>, <em class="parameter"><code>id</code></em> must be an unused name,
            or the name of an existing boolean occlusion query object.
            When <code class="function">glBeginQuery</code> is executed, the query object's samples-passed flag is reset to <code class="constant">GL_FALSE</code>.
            Subsequent rendering causes the flag to be set to <code class="constant">GL_TRUE</code> if any sample passes the depth test.  When
            <code class="function">glEndQuery</code> is executed, the samples-passed flag is assigned to the query object's result value.  This value can
            be queried by calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_RESULT</code>.
        </p><p>
            If <em class="parameter"><code>target</code></em> is <code class="constant">GL_PRIMITIVES_GENERATED</code>, <em class="parameter"><code>id</code></em> must be an unused
            name, or the name of an existing primitive query object previously bound to the <code class="constant">GL_PRIMITIVES_GENERATED</code> query binding.
            When <code class="function">glBeginQuery</code> is executed, the query object's primitives-generated counter is reset to 0.  Subsequent
            rendering will increment the counter once for every vertex that is emitted from the geometry shader, or from the vertex shader if
            no geometry shader is present.  When <code class="function">glEndQuery</code> is executed, the primitives-generated counter is assigned to
            the query object's result value.  This value can be queried by calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_RESULT</code>.
        </p><p>
            If <em class="parameter"><code>target</code></em> is <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, <em class="parameter"><code>id</code></em> must be
            an unused name, or the name of an existing primitive query object previously bound to the <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>
            query binding. When <code class="function">glBeginQuery</code> is executed, the query object's primitives-written counter is reset to 0.  Subsequent
            rendering will increment the counter once for every vertex that is written into the bound transform feedback buffer(s).  If transform feedback
            mode is not activated between the call to <code class="function">glBeginQuery</code> and <code class="function">glEndQuery</code>, the counter will not be
            incremented.  When <code class="function">glEndQuery</code> is executed, the primitives-written counter is assigned to
            the query object's result value.  This value can be queried by calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_RESULT</code>.
        </p><p>
            If <em class="parameter"><code>target</code></em> is <code class="constant">GL_TIME_ELAPSED</code>, <em class="parameter"><code>id</code></em> must be
            an unused name, or the name of an existing timer query object previously bound to the <code class="constant">GL_TIME_ELAPSED</code>
            query binding. When <code class="function">glBeginQuery</code> is executed, the query object's time counter is reset to 0.  When <code class="function">glEndQuery</code>
            is executed, the elapsed server time that has passed since the call to <code class="function">glBeginQuery</code> is written into the query object's
            time counter.  This value can be queried by calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_RESULT</code>.
        </p><p>
            Querying the <code class="constant">GL_QUERY_RESULT</code> implicitly flushes the GL pipeline until the rendering delimited by the
            query object has completed and the result is available.  <code class="constant">GL_QUERY_RESULT_AVAILABLE</code> can be queried to
            determine if the result is immediately available or if the rendering is not yet complete.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
            If the query target's count exceeds the maximum value representable in the number of available bits, as reported by
            <a href="glGetQueryiv.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryiv</span></span></a> with <em class="parameter"><code>target</code></em> set to the
            appropriate query target and <em class="parameter"><code>pname</code></em>
            <code class="constant">GL_QUERY_COUNTER_BITS</code>, the count becomes undefined.
        </p><p>
            An implementation may support 0 bits in its counter, in which case query results are always undefined
            and essentially useless.
        </p><p>
            When <code class="constant">GL_SAMPLE_BUFFERS</code> is 0, the samples-passed counter of an occlusion query will increment once for each
            fragment that passes the depth test.  When <code class="constant">GL_SAMPLE_BUFFERS</code> is 1, an implementation may either increment
            the samples-passed counter individually for each sample of a fragment that passes the depth test, or it may choose to increment
            the counter for all samples of a fragment if any one of them passes the depth test.
        </p><p>
            The query targets <code class="constant">GL_ANY_SAMPLES_PASSED</code>, and <code class="constant">GL_TIME_ELAPSED</code> are availale only if
            the GL version is 3.3 or higher.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> is not one of the accepted tokens.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginQuery</code> is executed while
            a query object of the same <em class="parameter"><code>target</code></em> is already active.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>
            is executed when a query object of the same <em class="parameter"><code>target</code></em> is not active.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>id</code></em> is 0.
        </p><p>
            <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.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>id</code></em> refers to an existing query object whose type
            does not does not match <em class="parameter"><code>target</code></em>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a href="glDeleteQueries.xml"><span class="citerefentry"><span class="refentrytitle">glDeleteQueries</span></span></a>,
            <a href="glGenQueries.xml"><span class="citerefentry"><span class="refentrytitle">glGenQueries</span></span></a>,
            <a href="glGetQueryiv.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryiv</span></span></a>,
            <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a>,
            <a href="glIsQuery.xml"><span class="citerefentry"><span class="refentrytitle">glIsQuery</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>© 2005 Addison-Wesley. 
            This material may be distributed subject to the terms and conditions set forth in 
            the Open Publication License, v 1.0, 8 June 1999.
            <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p></div></div></body></html>
