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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 $$ --> | |
29 | <refsect1 id="parameters"><title>Parameters</title> | |
30 | <variablelist> | |
31 | <varlistentry> | |
32 | <term><parameter>target</parameter></term> | |
33 | <listitem> | |
34 | <para> | |
35 | Specifies the target type of query object established between | |
36 | <function>glBeginQuery</function> and the subsequent <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry>. | |
37 | The symbolic constant must be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>, | |
38 | <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant>, | |
39 | <constant>GL_PRIMITIVES_GENERATED</constant>, <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or | |
40 | <constant>GL_TIME_ELAPSED</constant>. | |
41 | </para> | |
42 | </listitem> | |
43 | </varlistentry> | |
44 | <varlistentry> | |
45 | <term><parameter>id</parameter></term> | |
46 | <listitem> | |
47 | <para> | |
48 | Specifies the name of a query object. | |
49 | </para> | |
50 | </listitem> | |
51 | </varlistentry> | |
52 | </variablelist> | |
53 | </refsect1> | |
54 | <refsynopsisdiv><title>C Specification</title> | |
55 | <funcsynopsis> | |
56 | <funcprototype> | |
57 | <funcdef>void <function>glEndQuery</function></funcdef> | |
58 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
59 | </funcprototype> | |
60 | </funcsynopsis> | |
61 | </refsynopsisdiv> | |
62 | <!-- eqn: ignoring delim $$ --> | |
63 | <refsect1 id="parameters2"><title>Parameters</title> | |
64 | <variablelist> | |
65 | <varlistentry> | |
66 | <term><parameter>target</parameter></term> | |
67 | <listitem> | |
68 | <para> | |
69 | Specifies the target type of query object to be concluded. | |
70 | The symbolic constant must be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>, | |
71 | <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant>, | |
72 | <constant>GL_PRIMITIVES_GENERATED</constant>, <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or | |
73 | <constant>GL_TIME_ELAPSED</constant>. | |
74 | </para> | |
75 | </listitem> | |
76 | </varlistentry> | |
77 | </variablelist> | |
78 | </refsect1> | |
79 | <refsect1 id="description"><title>Description</title> | |
80 | <para> | |
81 | <function>glBeginQuery</function> and <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry> delimit the | |
82 | boundaries of a query object. <parameter>query</parameter> must be a name previously returned from a call to | |
83 | <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>. If a query object with name <parameter>id</parameter> | |
84 | does not yet exist it is created with the type determined by <parameter>target</parameter>. <parameter>target</parameter> must | |
85 | be one of <constant>GL_SAMPLES_PASSED</constant>, <constant>GL_ANY_SAMPLES_PASSED</constant>, <constant>GL_PRIMITIVES_GENERATED</constant>, | |
86 | <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, or <constant>GL_TIME_ELAPSED</constant>. The behavior of the query | |
87 | object depends on its type and is as follows. | |
88 | </para> | |
89 | <para> | |
90 | If <parameter>target</parameter> is <constant>GL_SAMPLES_PASSED</constant>, <parameter>id</parameter> must be an unused name, | |
91 | or the name of an existing occlusion query object. | |
92 | When <function>glBeginQuery</function> is executed, the query object's samples-passed counter is reset to 0. Subsequent | |
93 | rendering will increment the counter for every sample that passes the depth test. If the value of <constant>GL_SAMPLE_BUFFERS</constant> | |
94 | is 0, then the samples-passed count is incremented by 1 for each fragment. If the value of <constant>GL_SAMPLE_BUFFERS</constant> | |
95 | is 1, then the samples-passed count is incremented by the number of samples whose coverage bit is set. However, implementations, at their | |
96 | discression may instead increase the samples-passed count by the value of <constant>GL_SAMPLES</constant> if any sample in the fragment | |
97 | is covered. When <function>glEndQuery</function> | |
98 | is executed, the samples-passed counter is assigned to the query object's result value. This value can be queried by | |
99 | calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter> | |
100 | <constant>GL_QUERY_RESULT</constant>. | |
101 | </para> | |
102 | <para> | |
103 | If <parameter>target</parameter> is <constant>GL_ANY_SAMPLES_PASSED</constant> or <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant>, | |
104 | <parameter>id</parameter> must be an unused name, or the name of an existing boolean occlusion query object. | |
105 | When <function>glBeginQuery</function> is executed, the query object's samples-passed flag is reset to <constant>GL_FALSE</constant>. | |
106 | Subsequent rendering causes the flag to be set to <constant>GL_TRUE</constant> if any sample passes the depth test in the case of <constant>GL_ANY_SAMPLES_PASSED</constant>, | |
107 | or if the implementation determines that any sample might pass the depth test in the case of <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant>. | |
108 | The implementation may be able to provide a more efficient test in the case of <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant> | |
109 | if some false positives are acceptable to the application. When | |
110 | <function>glEndQuery</function> is executed, the samples-passed flag is assigned to the query object's result value. This value can | |
111 | be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter> | |
112 | <constant>GL_QUERY_RESULT</constant>. | |
113 | </para> | |
114 | <para> | |
115 | If <parameter>target</parameter> is <constant>GL_PRIMITIVES_GENERATED</constant>, <parameter>id</parameter> must be an unused | |
116 | name, or the name of an existing primitive query object previously bound to the <constant>GL_PRIMITIVES_GENERATED</constant> query binding. | |
117 | When <function>glBeginQuery</function> is executed, the query object's primitives-generated counter is reset to 0. Subsequent | |
118 | rendering will increment the counter once for every vertex that is emitted from the geometry shader, or from the vertex shader if | |
119 | no geometry shader is present. When <function>glEndQuery</function> is executed, the primitives-generated counter is assigned to | |
120 | the query object's result value. This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter> | |
121 | <constant>GL_QUERY_RESULT</constant>. | |
122 | </para> | |
123 | <para> | |
124 | If <parameter>target</parameter> is <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant>, <parameter>id</parameter> must be | |
125 | an unused name, or the name of an existing primitive query object previously bound to the <constant>GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</constant> | |
126 | query binding. When <function>glBeginQuery</function> is executed, the query object's primitives-written counter is reset to 0. Subsequent | |
127 | rendering will increment the counter once for every vertex that is written into the bound transform feedback buffer(s). If transform feedback | |
128 | mode is not activated between the call to <function>glBeginQuery</function> and <function>glEndQuery</function>, the counter will not be | |
129 | incremented. When <function>glEndQuery</function> is executed, the primitives-written counter is assigned to | |
130 | the query object's result value. This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter> | |
131 | <constant>GL_QUERY_RESULT</constant>. | |
132 | </para> | |
133 | <para> | |
134 | If <parameter>target</parameter> is <constant>GL_TIME_ELAPSED</constant>, <parameter>id</parameter> must be | |
135 | an unused name, or the name of an existing timer query object previously bound to the <constant>GL_TIME_ELAPSED</constant> | |
136 | query binding. When <function>glBeginQuery</function> is executed, the query object's time counter is reset to 0. When <function>glEndQuery</function> | |
137 | is executed, the elapsed server time that has passed since the call to <function>glBeginQuery</function> is written into the query object's | |
138 | time counter. This value can be queried by calling <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry> with <parameter>pname</parameter> | |
139 | <constant>GL_QUERY_RESULT</constant>. | |
140 | </para> | |
141 | <para> | |
142 | Querying the <constant>GL_QUERY_RESULT</constant> implicitly flushes the GL pipeline until the rendering delimited by the | |
143 | query object has completed and the result is available. <constant>GL_QUERY_RESULT_AVAILABLE</constant> can be queried to | |
144 | determine if the result is immediately available or if the rendering is not yet complete. | |
145 | </para> | |
146 | </refsect1> | |
147 | <refsect1 id="notes"><title>Notes</title> | |
148 | <para> | |
149 | If the query target's count exceeds the maximum value representable in the number of available bits, as reported by | |
150 | <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry> with <parameter>target</parameter> set to the | |
151 | appropriate query target and <parameter>pname</parameter> | |
152 | <constant>GL_QUERY_COUNTER_BITS</constant>, the count becomes undefined. | |
153 | </para> | |
154 | <para> | |
155 | An implementation may support 0 bits in its counter, in which case query results are always undefined | |
156 | and essentially useless. | |
157 | </para> | |
158 | <para> | |
159 | When <constant>GL_SAMPLE_BUFFERS</constant> is 0, the samples-passed counter of an occlusion query will increment once for each | |
160 | fragment that passes the depth test. When <constant>GL_SAMPLE_BUFFERS</constant> is 1, an implementation may either increment | |
161 | the samples-passed counter individually for each sample of a fragment that passes the depth test, or it may choose to increment | |
162 | the counter for all samples of a fragment if any one of them passes the depth test. | |
163 | </para> | |
164 | <para> | |
165 | The query targets <constant>GL_ANY_SAMPLES_PASSED</constant>, and <constant>GL_TIME_ELAPSED</constant> are availale only if | |
166 | the GL version is 3.3 or higher. | |
167 | </para> | |
168 | <para> | |
169 | The query target <constant>GL_ANY_SAMPLES_PASSED_CONSERVATIVE</constant> is available only of the GL version is 4.3 or higher. | |
170 | </para> | |
171 | </refsect1> | |
172 | <refsect1 id="errors"><title>Errors</title> | |
173 | <para> | |
174 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the accepted tokens. | |
175 | </para> | |
176 | <para> | |
177 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginQuery</function> is executed while | |
178 | a query object of the same <parameter>target</parameter> is already active. | |
179 | </para> | |
180 | <para> | |
181 | <constant>GL_INVALID_OPERATION</constant> is generated if <citerefentry><refentrytitle>glEndQuery</refentrytitle></citerefentry> | |
182 | is executed when a query object of the same <parameter>target</parameter> is not active. | |
183 | </para> | |
184 | <para> | |
185 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is 0. | |
186 | </para> | |
187 | <para> | |
188 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is the name of an already active query object. | |
189 | </para> | |
190 | <para> | |
191 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> refers to an existing query object whose type | |
192 | does not does not match <parameter>target</parameter>. | |
193 | </para> | |
194 | </refsect1> | |
195 | <refsect1 id="seealso"><title>See Also</title> | |
196 | <para> | |
197 | <citerefentry><refentrytitle>glDeleteQueries</refentrytitle></citerefentry>, | |
198 | <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>, | |
199 | <citerefentry><refentrytitle>glGetQueryiv</refentrytitle></citerefentry>, | |
200 | <citerefentry><refentrytitle>glGetQueryObject</refentrytitle></citerefentry>, | |
201 | <citerefentry><refentrytitle>glIsQuery</refentrytitle></citerefentry> | |
202 | </para> | |
203 | </refsect1> | |
204 | <refsect1 id="Copyright"><title>Copyright</title> | |
205 | <para> | |
206 | Copyright <trademark class="copyright"></trademark> 2005 Addison-Wesley. | |
207 | Copyright <trademark class="copyright"></trademark> 2010-2012 Khronos Group. | |
208 | This material may be distributed subject to the terms and conditions set forth in | |
209 | the Open Publication License, v 1.0, 8 June 1999. | |
210 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>. | |
211 | </para> | |
212 | </refsect1> | |
213 | </refentry> |