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1 | <?xml version="1.0" encoding="UTF-8"?> |
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4 | <?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> | |
5 | Specifies the target type of query object established between | |
6 | <code class="function">glBeginQuery</code> and the subsequent <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a>. | |
7 | The symbolic constant must be one of <code class="constant">GL_SAMPLES_PASSED</code>, <code class="constant">GL_ANY_SAMPLES_PASSED</code>, | |
8 | <code class="constant">GL_PRIMITIVES_GENERATED</code>, <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or | |
9 | <code class="constant">GL_TIME_ELAPSED</code>. | |
10 | </p></dd><dt><span class="term"><em class="parameter"><code>id</code></em></span></dt><dd><p> | |
11 | Specifies the name of a query object. | |
12 | </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> | |
13 | Specifies the target type of query object to be concluded. | |
14 | The symbolic constant must be one of <code class="constant">GL_SAMPLES_PASSED</code>, <code class="constant">GL_ANY_SAMPLES_PASSED</code>, | |
15 | <code class="constant">GL_PRIMITIVES_GENERATED</code>, <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or | |
16 | <code class="constant">GL_TIME_ELAPSED</code>. | |
17 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
18 | <code class="function">glBeginQuery</code> and <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a> delimit the | |
19 | boundaries of a query object. <em class="parameter"><code>query</code></em> must be a name previously returned from a call to | |
20 | <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> | |
21 | 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 | |
22 | 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>, | |
23 | <code class="constant">GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>, or <code class="constant">GL_TIME_ELAPSED</code>. The behavior of the query | |
24 | object depends on its type and is as follows. | |
25 | </p><p> | |
26 | 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, | |
27 | or the name of an existing occlusion query object. | |
28 | When <code class="function">glBeginQuery</code> is executed, the query object's samples-passed counter is reset to 0. Subsequent | |
29 | rendering will increment the counter for every sample that passes the depth test. If the value of <code class="constant">GL_SAMPLE_BUFFERS</code> | |
30 | 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> | |
31 | is 1, then the samples-passed count is incremented by the number of samples whose coverage bit is set. However, implementations, at their | |
32 | discression may instead increase the samples-passed count by the value of <code class="constant">GL_SAMPLES</code> if any sample in the fragment | |
33 | is covered. When <code class="function">glEndQuery</code> | |
34 | is executed, the samples-passed counter is assigned to the query object's result value. This value can be queried by | |
35 | calling <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a> with <em class="parameter"><code>pname</code></em> | |
36 | <code class="constant">GL_QUERY_RESULT</code>. | |
37 | </p><p> | |
38 | 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, | |
39 | or the name of an existing boolean occlusion query object. | |
40 | When <code class="function">glBeginQuery</code> is executed, the query object's samples-passed flag is reset to <code class="constant">GL_FALSE</code>. | |
41 | Subsequent rendering causes the flag to be set to <code class="constant">GL_TRUE</code> if any sample passes the depth test. When | |
42 | <code class="function">glEndQuery</code> is executed, the samples-passed flag is assigned to the query object's result value. This value can | |
43 | 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> | |
44 | <code class="constant">GL_QUERY_RESULT</code>. | |
45 | </p><p> | |
46 | 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 | |
47 | name, or the name of an existing primitive query object previously bound to the <code class="constant">GL_PRIMITIVES_GENERATED</code> query binding. | |
48 | When <code class="function">glBeginQuery</code> is executed, the query object's primitives-generated counter is reset to 0. Subsequent | |
49 | rendering will increment the counter once for every vertex that is emitted from the geometry shader, or from the vertex shader if | |
50 | no geometry shader is present. When <code class="function">glEndQuery</code> is executed, the primitives-generated counter is assigned to | |
51 | 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> | |
52 | <code class="constant">GL_QUERY_RESULT</code>. | |
53 | </p><p> | |
54 | 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 | |
55 | 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> | |
56 | query binding. When <code class="function">glBeginQuery</code> is executed, the query object's primitives-written counter is reset to 0. Subsequent | |
57 | rendering will increment the counter once for every vertex that is written into the bound transform feedback buffer(s). If transform feedback | |
58 | mode is not activated between the call to <code class="function">glBeginQuery</code> and <code class="function">glEndQuery</code>, the counter will not be | |
59 | incremented. When <code class="function">glEndQuery</code> is executed, the primitives-written counter is assigned to | |
60 | 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> | |
61 | <code class="constant">GL_QUERY_RESULT</code>. | |
62 | </p><p> | |
63 | 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 | |
64 | an unused name, or the name of an existing timer query object previously bound to the <code class="constant">GL_TIME_ELAPSED</code> | |
65 | 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> | |
66 | 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 | |
67 | 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> | |
68 | <code class="constant">GL_QUERY_RESULT</code>. | |
69 | </p><p> | |
70 | Querying the <code class="constant">GL_QUERY_RESULT</code> implicitly flushes the GL pipeline until the rendering delimited by the | |
71 | query object has completed and the result is available. <code class="constant">GL_QUERY_RESULT_AVAILABLE</code> can be queried to | |
72 | determine if the result is immediately available or if the rendering is not yet complete. | |
73 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> | |
74 | If the query target's count exceeds the maximum value representable in the number of available bits, as reported by | |
75 | <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 | |
76 | appropriate query target and <em class="parameter"><code>pname</code></em> | |
77 | <code class="constant">GL_QUERY_COUNTER_BITS</code>, the count becomes undefined. | |
78 | </p><p> | |
79 | An implementation may support 0 bits in its counter, in which case query results are always undefined | |
80 | and essentially useless. | |
81 | </p><p> | |
82 | When <code class="constant">GL_SAMPLE_BUFFERS</code> is 0, the samples-passed counter of an occlusion query will increment once for each | |
83 | fragment that passes the depth test. When <code class="constant">GL_SAMPLE_BUFFERS</code> is 1, an implementation may either increment | |
84 | the samples-passed counter individually for each sample of a fragment that passes the depth test, or it may choose to increment | |
85 | the counter for all samples of a fragment if any one of them passes the depth test. | |
86 | </p><p> | |
87 | The query targets <code class="constant">GL_ANY_SAMPLES_PASSED</code>, and <code class="constant">GL_TIME_ELAPSED</code> are availale only if | |
88 | the GL version is 3.3 or higher. | |
89 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
90 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> is not one of the accepted tokens. | |
91 | </p><p> | |
92 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glBeginQuery</code> is executed while | |
93 | a query object of the same <em class="parameter"><code>target</code></em> is already active. | |
94 | </p><p> | |
95 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <a href="glEndQuery.xml"><span class="citerefentry"><span class="refentrytitle">glEndQuery</span></span></a> | |
96 | is executed when a query object of the same <em class="parameter"><code>target</code></em> is not active. | |
97 | </p><p> | |
98 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>id</code></em> is 0. | |
99 | </p><p> | |
100 | <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. | |
101 | </p><p> | |
102 | <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 | |
103 | does not does not match <em class="parameter"><code>target</code></em>. | |
104 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
105 | <a href="glDeleteQueries.xml"><span class="citerefentry"><span class="refentrytitle">glDeleteQueries</span></span></a>, | |
106 | <a href="glGenQueries.xml"><span class="citerefentry"><span class="refentrytitle">glGenQueries</span></span></a>, | |
107 | <a href="glGetQueryiv.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryiv</span></span></a>, | |
108 | <a href="glGetQueryObject.xml"><span class="citerefentry"><span class="refentrytitle">glGetQueryObject</span></span></a>, | |
109 | <a href="glIsQuery.xml"><span class="citerefentry"><span class="refentrytitle">glIsQuery</span></span></a> | |
110 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
111 | Copyright <span class="trademark"></span>© 2005 Addison-Wesley. | |
112 | This material may be distributed subject to the terms and conditions set forth in | |
113 | the Open Publication License, v 1.0, 8 June 1999. | |
114 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
115 | </p></div></div></body></html> |