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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="glBeginConditionalRender"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>2010</year> | |
9 | <holder>Khronos Group</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glBeginConditionalRender</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glBeginConditionalRender</refname> | |
17 | <refpurpose>start conditional rendering</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glBeginConditionalRender</function></funcdef> | |
23 | <paramdef>GLuint <parameter>id</parameter></paramdef> | |
24 | <paramdef>GLenum <parameter>mode</parameter></paramdef> | |
25 | </funcprototype> | |
26 | </funcsynopsis> | |
27 | </refsynopsisdiv> | |
28 | <refsect1 id="parameters"><title>Parameters</title> | |
29 | <variablelist> | |
30 | <varlistentry> | |
31 | <term><parameter>id</parameter></term> | |
32 | <listitem> | |
33 | <para> | |
34 | Specifies the name of an occlusion query object whose results are used to determine if the rendering commands are discarded. | |
35 | </para> | |
36 | </listitem> | |
37 | </varlistentry> | |
38 | <varlistentry> | |
39 | <term><parameter>mode</parameter></term> | |
40 | <listitem> | |
41 | <para> | |
42 | Specifies how <function>glBeginConditionalRender</function> interprets the results of the occlusion query. | |
43 | </para> | |
44 | </listitem> | |
45 | </varlistentry> | |
46 | </variablelist> | |
47 | </refsect1> | |
48 | <refsynopsisdiv><title>C Specification</title> | |
49 | <funcsynopsis> | |
50 | <funcprototype> | |
51 | <funcdef>void <function>glEndConditionalRender</function></funcdef> | |
52 | <paramdef><parameter>void</parameter></paramdef> | |
53 | </funcprototype> | |
54 | </funcsynopsis> | |
55 | </refsynopsisdiv> | |
56 | <refsect1 id="description"><title>Description</title> | |
57 | <para> | |
58 | Conditional rendering is started using <function>glBeginConditionalRender</function> and ended using <function>glEndConditionalRender</function>. | |
59 | During conditional rendering, all vertex array commands, as well as <citerefentry><refentrytitle>glClear</refentrytitle></citerefentry> and | |
60 | <citerefentry><refentrytitle>glClearBuffer</refentrytitle></citerefentry> have no effect if the (<constant>GL_SAMPLES_PASSED</constant>) result | |
61 | of the query object <parameter>id</parameter> is zero, or if the (<constant>GL_ANY_SAMPLES_PASSED</constant>) result is <constant>GL_FALSE</constant>. | |
62 | The results of commands setting the current vertex state, such as <citerefentry><refentrytitle>glVertexAttrib</refentrytitle></citerefentry> are | |
63 | undefined. If the (<constant>GL_SAMPLES_PASSED</constant>) result is non-zero or if the (<constant>GL_ANY_SAMPLES_PASSED</constant>) result is | |
64 | <constant>GL_TRUE</constant>, such commands are not discarded. The <parameter>id</parameter> parameter to <function>glBeginConditionalRender</function> | |
65 | must be the name of a query object previously returned from a call to <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>. | |
66 | <parameter>mode</parameter> specifies how the results of the query object are to be interpreted. If <parameter>mode</parameter> is | |
67 | <constant>GL_QUERY_WAIT</constant>, the GL waits for the results of the query to be available and then uses the results to determine if subsequent | |
68 | rendering commands are discarded. If <parameter>mode</parameter> is <constant>GL_QUERY_NO_WAIT</constant>, the GL may choose to unconditionally | |
69 | execute the subsequent rendering commands without waiting for the query to complete. | |
70 | </para> | |
71 | <para> | |
72 | If <parameter>mode</parameter> is <constant>GL_QUERY_BY_REGION_WAIT</constant>, the GL will also wait for occlusion query results and discard | |
73 | rendering commands if the result of the occlusion query is zero. If the query result is non-zero, subsequent rendering commands are executed, | |
74 | but the GL may discard the results of the commands for any region of the framebuffer that did not contribute to the sample count in the specified | |
75 | occlusion query. Any such discarding is done in an implementation-dependent manner, but the rendering command results may not be discarded for | |
76 | any samples that contributed to the occlusion query sample count. If <parameter>mode</parameter> is <constant>GL_QUERY_BY_REGION_NO_WAIT</constant>, | |
77 | the GL operates as in <constant>GL_QUERY_BY_REGION_WAIT</constant>, but may choose to unconditionally execute the subsequent rendering commands | |
78 | without waiting for the query to complete. | |
79 | </para> | |
80 | </refsect1> | |
81 | <refsect1 id="notes"><title>Notes</title> | |
82 | <para> | |
83 | <function>glBeginConditionalRender</function> and <function>glEndConditionalRender</function> are available only if the GL version is 3.0 or greater. | |
84 | </para> | |
85 | <para> | |
86 | The <constant>GL_ANY_SAMPLES_PASSED</constant> query result is available only if the GL version is 3.3 or greater. | |
87 | </para> | |
88 | </refsect1> | |
89 | <refsect1 id="errors"><title>Errors</title> | |
90 | <para> | |
91 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>id</parameter> is not the name of an existing query object. | |
92 | </para> | |
93 | <para> | |
94 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not one of the accepted tokens. | |
95 | </para> | |
96 | <para> | |
97 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginConditionalRender</function> is called while conditional rendering is active, | |
98 | or if <function>glEndConditionalRender</function> is called while conditional rendering is inactive. | |
99 | </para> | |
100 | <para> | |
101 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is the name of a query object with a target other than | |
102 | <constant>GL_SAMPLES_PASSED</constant> or <constant>GL_ANY_SAMPLES_PASSED</constant>. | |
103 | </para> | |
104 | <para> | |
105 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>id</parameter> is the name of a query currently in progress. | |
106 | </para> | |
107 | </refsect1> | |
108 | <refsect1 id="seealso"><title>See Also</title> | |
109 | <para> | |
110 | <citerefentry><refentrytitle>glGenQueries</refentrytitle></citerefentry>, | |
111 | <citerefentry><refentrytitle>glDeleteQueries</refentrytitle></citerefentry>, | |
112 | <citerefentry><refentrytitle>glBeginQuery</refentrytitle></citerefentry> | |
113 | </para> | |
114 | </refsect1> | |
115 | <refsect1 id="Copyright"><title>Copyright</title> | |
116 | <para> | |
117 | Copyright <trademark class="copyright"></trademark> 2009 Khronos Group. | |
118 | This material may be distributed subject to the terms and conditions set forth in | |
119 | the Open Publication License, v 1.0, 8 June 1999. | |
120 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>. | |
121 | </para> | |
122 | </refsect1> | |
123 | </refentry> |