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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="glGetActiveUniformBlock"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>2010</year> | |
9 | <holder>Khronos Group</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glGetActiveUniformBlock</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glGetActiveUniformBlock</refname> | |
17 | <refpurpose>query information about an active uniform block</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glGetActiveUniformBlockiv</function></funcdef> | |
23 | <paramdef>GLuint <parameter>program</parameter></paramdef> | |
24 | <paramdef>GLuint <parameter>uniformBlockIndex</parameter></paramdef> | |
25 | <paramdef>GLenum <parameter>pname</parameter></paramdef> | |
26 | <paramdef>GLint <parameter>params</parameter></paramdef> | |
27 | </funcprototype> | |
28 | </funcsynopsis> | |
29 | </refsynopsisdiv> | |
30 | <refsect1 id="parameters"><title>Parameters</title> | |
31 | <variablelist> | |
32 | <varlistentry> | |
33 | <term><parameter>program</parameter></term> | |
34 | <listitem> | |
35 | <para> | |
36 | Specifies the name of a program containing the uniform block. | |
37 | </para> | |
38 | </listitem> | |
39 | </varlistentry> | |
40 | <varlistentry> | |
41 | <term><parameter>uniformBlockIndex</parameter></term> | |
42 | <listitem> | |
43 | <para> | |
44 | Specifies the index of the uniform block within <parameter>program</parameter>. | |
45 | </para> | |
46 | </listitem> | |
47 | </varlistentry> | |
48 | <varlistentry> | |
49 | <term><parameter>pname</parameter></term> | |
50 | <listitem> | |
51 | <para> | |
52 | Specifies the name of the parameter to query. | |
53 | </para> | |
54 | </listitem> | |
55 | </varlistentry> | |
56 | <varlistentry> | |
57 | <term><parameter>params</parameter></term> | |
58 | <listitem> | |
59 | <para> | |
60 | Specifies the address of a variable to receive the result of the query. | |
61 | </para> | |
62 | </listitem> | |
63 | </varlistentry> | |
64 | </variablelist> | |
65 | </refsect1> | |
66 | <refsect1 id="description"><title>Description</title> | |
67 | <para> | |
68 | <function>glGetActiveUniformBlockiv</function> retrieves information about an active uniform block within <parameter>program</parameter>. | |
69 | </para> | |
70 | <para> | |
71 | <parameter>program</parameter> must be the name of a program object for which the command | |
72 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> must have been called in the past, although it is not required that | |
73 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> must have succeeded. The link could have failed because the number | |
74 | of active uniforms exceeded the limit. | |
75 | </para> | |
76 | <para> | |
77 | <parameter>uniformBlockIndex</parameter> is an active uniform block index of <parameter>program</parameter>, and must be less than the value | |
78 | of <constant>GL_ACTIVE_UNIFORM_BLOCKS</constant>. | |
79 | </para> | |
80 | <para> | |
81 | Upon success, the uniform block parameter(s) specified by <parameter>pname</parameter> are returned in <parameter>params</parameter>. If an error | |
82 | occurs, nothing will be written to <parameter>params</parameter>. | |
83 | </para> | |
84 | <para> | |
85 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_BINDING</constant>, then the index of the uniform buffer binding point | |
86 | last selected by the uniform block specified by <parameter>uniformBlockIndex</parameter> for <parameter>program</parameter> is returned. If | |
87 | no uniform block has been previously specified, zero is returned. | |
88 | </para> | |
89 | <para> | |
90 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_DATA_SIZE</constant>, then the implementation-dependent minimum total buffer | |
91 | object size, in basic machine units, required to hold all active uniforms in the uniform block identified by <parameter>uniformBlockIndex</parameter> | |
92 | is returned. It is neither guaranteed nor expected that a given implementation will arrange uniform values as tightly packed in a buffer | |
93 | object. The exception to this is the <emphasis>std140 uniform block layout</emphasis>, which guarantees specific packing behavior and does not | |
94 | require the application to query for offsets and strides. In this case the minimum size may still be queried, even though it is determined in | |
95 | advance based only on the uniform block declaration. | |
96 | </para> | |
97 | <para> | |
98 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_NAME_LENGTH</constant>, then the total length (including the nul terminator) of | |
99 | the name of the uniform block identified by <parameter>uniformBlockIndex</parameter> is returned. | |
100 | </para> | |
101 | <para> | |
102 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS</constant>, then the number of active uniforms in the uniform | |
103 | block identified by <parameter>uniformBlockIndex</parameter> is returned. | |
104 | </para> | |
105 | <para> | |
106 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES</constant>, then a list of the active uniform indices | |
107 | for the uniform block identified by <parameter>uniformBlockIndex</parameter> is returned. The number of elements that will be written to | |
108 | <parameter>params</parameter> is the value of <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS</constant> for <parameter>uniformBlockIndex</parameter>. | |
109 | </para> | |
110 | <para> | |
111 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_VERTEX_SHADER</constant>, <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_TESS_CONTROL_SHADER</constant>, | |
112 | <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_TESS_EVALUATION_SHADER</constant>, <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_GEOMETRY_SHADER</constant>, | |
113 | <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER</constant>, or <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER</constant> | |
114 | then a boolean value indicating whether the uniform block identified by | |
115 | <parameter>uniformBlockIndex</parameter> is referenced by the vertex, tessellation control, tessellation evaluation, geometry, fragment or compute | |
116 | programming stages of program, respectively, is returned. | |
117 | </para> | |
118 | </refsect1> | |
119 | <refsect1 id="errors"><title>Errors</title> | |
120 | <para> | |
121 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>uniformBlockIndex</parameter> is greater than or equal to the value | |
122 | of <constant>GL_ACTIVE_UNIFORM_BLOCKS</constant> or is not the index of an active uniform block in <parameter>program</parameter>. | |
123 | </para> | |
124 | <para> | |
125 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not one of the accepted tokens. | |
126 | </para> | |
127 | <para> | |
128 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>program</parameter> is not the name of a program object for which | |
129 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> has been called in the past. | |
130 | </para> | |
131 | </refsect1> | |
132 | <refsect1 id="notes"><title>Notes</title> | |
133 | <para> | |
134 | <function>glGetActiveUniformBlockiv</function> is available only if the GL version is 3.1 or greater. | |
135 | </para> | |
136 | <para> | |
137 | <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER</constant> is accepted only if the GL version is 4.3 | |
138 | or greater. | |
139 | </para> | |
140 | </refsect1> | |
141 | <refsect1 id="seealso"><title>See Also</title> | |
142 | <para> | |
143 | <citerefentry><refentrytitle>glGetActiveUniformBlockName</refentrytitle></citerefentry>, | |
144 | <citerefentry><refentrytitle>glGetUniformBlockIndex</refentrytitle></citerefentry>, | |
145 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> | |
146 | </para> | |
147 | </refsect1> | |
148 | <refsect1 id="Copyright"><title>Copyright</title> | |
149 | <para> | |
150 | Copyright <trademark class="copyright"></trademark> 2010 Khronos Group. | |
151 | This material may be distributed subject to the terms and conditions set forth in | |
152 | the Open Publication License, v 1.0, 8 June 1999. | |
153 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>. | |
154 | </para> | |
155 | </refsect1> | |
156 | </refentry> |