| 1 | <?xml version="1.0" encoding="UTF-8"?>\r |
| 2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"\r |
| 3 | "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">\r |
| 4 | <refentry id="glGetActiveUniformBlock">\r |
| 5 | <refmeta>\r |
| 6 | <refmetainfo>\r |
| 7 | <copyright>\r |
| 8 | <year>2010</year>\r |
| 9 | <holder>Khronos Group</holder>\r |
| 10 | </copyright>\r |
| 11 | </refmetainfo>\r |
| 12 | <refentrytitle>glGetActiveUniformBlock</refentrytitle>\r |
| 13 | <manvolnum>3G</manvolnum>\r |
| 14 | </refmeta>\r |
| 15 | <refnamediv>\r |
| 16 | <refname>glGetActiveUniformBlock</refname>\r |
| 17 | <refpurpose>query information about an active uniform block</refpurpose>\r |
| 18 | </refnamediv>\r |
| 19 | <refsynopsisdiv><title>C Specification</title>\r |
| 20 | <funcsynopsis>\r |
| 21 | <funcprototype>\r |
| 22 | <funcdef>void <function>glGetActiveUniformBlockiv</function></funcdef>\r |
| 23 | <paramdef>GLuint <parameter>program</parameter></paramdef>\r |
| 24 | <paramdef>GLuint <parameter>uniformBlockIndex</parameter></paramdef>\r |
| 25 | <paramdef>GLenum <parameter>pname</parameter></paramdef>\r |
| 26 | <paramdef>GLint <parameter>params</parameter></paramdef>\r |
| 27 | </funcprototype>\r |
| 28 | </funcsynopsis>\r |
| 29 | </refsynopsisdiv>\r |
| 30 | <refsect1 id="parameters"><title>Parameters</title>\r |
| 31 | <variablelist>\r |
| 32 | <varlistentry>\r |
| 33 | <term><parameter>program</parameter></term>\r |
| 34 | <listitem>\r |
| 35 | <para>\r |
| 36 | Specifies the name of a program containing the uniform block.\r |
| 37 | </para>\r |
| 38 | </listitem>\r |
| 39 | </varlistentry>\r |
| 40 | <varlistentry>\r |
| 41 | <term><parameter>uniformBlockIndex</parameter></term>\r |
| 42 | <listitem>\r |
| 43 | <para>\r |
| 44 | Specifies the index of the uniform block within <parameter>program</parameter>.\r |
| 45 | </para>\r |
| 46 | </listitem>\r |
| 47 | </varlistentry>\r |
| 48 | <varlistentry>\r |
| 49 | <term><parameter>pname</parameter></term>\r |
| 50 | <listitem>\r |
| 51 | <para>\r |
| 52 | Specifies the name of the parameter to query.\r |
| 53 | </para>\r |
| 54 | </listitem>\r |
| 55 | </varlistentry>\r |
| 56 | <varlistentry>\r |
| 57 | <term><parameter>params</parameter></term>\r |
| 58 | <listitem>\r |
| 59 | <para>\r |
| 60 | Specifies the address of a variable to receive the result of the query.\r |
| 61 | </para>\r |
| 62 | </listitem>\r |
| 63 | </varlistentry>\r |
| 64 | </variablelist>\r |
| 65 | </refsect1>\r |
| 66 | <refsect1 id="description"><title>Description</title>\r |
| 67 | <para>\r |
| 68 | <function>glGetActiveUniformBlockiv</function> retrieves information about an active uniform block within <parameter>program</parameter>.\r |
| 69 | </para>\r |
| 70 | <para>\r |
| 71 | <parameter>program</parameter> must be the name of a program object for which the command\r |
| 72 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> must have been called in the past, although it is not required that\r |
| 73 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> must have succeeded. The link could have failed because the number\r |
| 74 | of active uniforms exceeded the limit.\r |
| 75 | </para>\r |
| 76 | <para>\r |
| 77 | <parameter>uniformBlockIndex</parameter> is an active uniform block index of <parameter>program</parameter>, and must be less than the value\r |
| 78 | of <constant>GL_ACTIVE_UNIFORM_BLOCKS</constant>.\r |
| 79 | </para>\r |
| 80 | <para>\r |
| 81 | Upon success, the uniform block parameter(s) specified by <parameter>pname</parameter> are returned in <parameter>params</parameter>. If an error\r |
| 82 | occurs, nothing will be written to <parameter>params</parameter>.\r |
| 83 | </para>\r |
| 84 | <para>\r |
| 85 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_BINDING</constant>, then the index of the uniform buffer binding point\r |
| 86 | last selected by the uniform block specified by <parameter>uniformBlockIndex</parameter> for <parameter>program</parameter> is returned. If\r |
| 87 | no uniform block has been previously specified, zero is returned.\r |
| 88 | </para>\r |
| 89 | <para>\r |
| 90 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_DATA_SIZE</constant>, then the implementation-dependent minimum total buffer\r |
| 91 | object size, in basic machine units, required to hold all active uniforms in the uniform block identified by <parameter>uniformBlockIndex</parameter>\r |
| 92 | is returned. It is neither guaranteed nor expected that a given implementation will arrange uniform values as tightly packed in a buffer\r |
| 93 | object. The exception to this is the <emphasis>std140 uniform block layout</emphasis>, which guarantees specific packing behavior and does not\r |
| 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\r |
| 95 | advance based only on the uniform block declaration.\r |
| 96 | </para>\r |
| 97 | <para>\r |
| 98 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_NAME_LENGTH</constant>, then the total length (including the nul terminator) of\r |
| 99 | the name of the uniform block identified by <parameter>uniformBlockIndex</parameter> is returned.\r |
| 100 | </para>\r |
| 101 | <para>\r |
| 102 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS</constant>, then the number of active uniforms in the uniform\r |
| 103 | block identified by <parameter>uniformBlockIndex</parameter> is returned.\r |
| 104 | </para>\r |
| 105 | <para>\r |
| 106 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES</constant>, then a list of the active uniform indices\r |
| 107 | for the uniform block identified by <parameter>uniformBlockIndex</parameter> is returned. The number of elements that will be written to\r |
| 108 | <parameter>params</parameter> is the value of <constant>GL_UNIFORM_BLOCK_ACTIVE_UNIFORMS</constant> for <parameter>uniformBlockIndex</parameter>.\r |
| 109 | </para>\r |
| 110 | <para>\r |
| 111 | If <parameter>pname</parameter> is <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_VERTEX_SHADER</constant>, <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_GEOMETRY_SHADER</constant>,\r |
| 112 | or <constant>GL_UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER</constant>, then a boolean value indicating whether the uniform block identified by\r |
| 113 | <parameter>uniformBlockIndex</parameter> is referenced by the vertex, geometry, or fragment programming stages of program, respectively, is returned.\r |
| 114 | </para>\r |
| 115 | </refsect1>\r |
| 116 | <refsect1 id="errors"><title>Errors</title>\r |
| 117 | <para>\r |
| 118 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>uniformBlockIndex</parameter> is greater than or equal to the value\r |
| 119 | of <constant>GL_ACTIVE_UNIFORM_BLOCKS</constant> or is not the index of an active uniform block in <parameter>program</parameter>.\r |
| 120 | </para>\r |
| 121 | <para>\r |
| 122 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>pname</parameter> is not one of the accepted tokens.\r |
| 123 | </para>\r |
| 124 | <para>\r |
| 125 | <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>program</parameter> is not the name of a program object for which\r |
| 126 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry> has been called in the past.\r |
| 127 | </para>\r |
| 128 | </refsect1>\r |
| 129 | <refsect1 id="notes"><title>Notes</title>\r |
| 130 | <para>\r |
| 131 | <function>glGetActiveUniformBlockiv</function> is available only if the GL version is 3.1 or greater.\r |
| 132 | </para>\r |
| 133 | </refsect1>\r |
| 134 | <refsect1 id="seealso"><title>See Also</title>\r |
| 135 | <para>\r |
| 136 | <citerefentry><refentrytitle>glGetActiveUniformBlockName</refentrytitle></citerefentry>,\r |
| 137 | <citerefentry><refentrytitle>glGetUniformBlockIndex</refentrytitle></citerefentry>,\r |
| 138 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>\r |
| 139 | </para>\r |
| 140 | </refsect1>\r |
| 141 | <refsect1 id="Copyright"><title>Copyright</title>\r |
| 142 | <para>\r |
| 143 | Copyright <trademark class="copyright"></trademark> 2010 Khronos Group. \r |
| 144 | This material may be distributed subject to the terms and conditions set forth in \r |
| 145 | the Open Publication License, v 1.0, 8 June 1999.\r |
| 146 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r |
| 147 | </para>\r |
| 148 | </refsect1>\r |
| 149 | </refentry>\r |