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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> |