| 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="glBeginTransformFeedback">\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>glBeginTransformFeedback</refentrytitle>\r |
| 13 | <manvolnum>3G</manvolnum>\r |
| 14 | </refmeta>\r |
| 15 | <refnamediv>\r |
| 16 | <refname>glBeginTransformFeedback</refname>\r |
| 17 | <refpurpose>start transform feedback operation</refpurpose>\r |
| 18 | </refnamediv>\r |
| 19 | <refsynopsisdiv><title>C Specification</title>\r |
| 20 | <funcsynopsis>\r |
| 21 | <funcprototype>\r |
| 22 | <funcdef>void <function>glBeginTransformFeedback</function></funcdef>\r |
| 23 | <paramdef>GLenum <parameter>primitiveMode</parameter></paramdef>\r |
| 24 | </funcprototype>\r |
| 25 | </funcsynopsis>\r |
| 26 | </refsynopsisdiv>\r |
| 27 | <refsect1 id="parameters"><title>Parameters</title>\r |
| 28 | <variablelist>\r |
| 29 | <varlistentry>\r |
| 30 | <term><parameter>primitiveMode</parameter></term>\r |
| 31 | <listitem>\r |
| 32 | <para>\r |
| 33 | Specify the output type of the primitives that will be recorded into the\r |
| 34 | buffer objects that are bound for transform feedback.\r |
| 35 | </para>\r |
| 36 | </listitem>\r |
| 37 | </varlistentry>\r |
| 38 | </variablelist>\r |
| 39 | </refsect1>\r |
| 40 | <refsynopsisdiv><title>C Specification</title>\r |
| 41 | <funcsynopsis>\r |
| 42 | <funcprototype>\r |
| 43 | <funcdef>void <function>glEndTransformFeedback</function></funcdef>\r |
| 44 | <paramdef><parameter>void</parameter></paramdef>\r |
| 45 | </funcprototype>\r |
| 46 | </funcsynopsis>\r |
| 47 | </refsynopsisdiv>\r |
| 48 | <refsect1 id="description"><title>Description</title>\r |
| 49 | <para>\r |
| 50 | Transform feedback mode captures the values of varying variables written by the vertex shader (or, if active, the geometry shader).\r |
| 51 | Transform feedback is said to be active after a call to <function>glBeginTransformFeedback</function>\r |
| 52 | until a subsequent call to <citerefentry><refentrytitle>glEndTransformFeedback</refentrytitle></citerefentry>.\r |
| 53 | Transform feedback commands must be paired.\r |
| 54 | </para>\r |
| 55 | <para>\r |
| 56 | If no geometry shader is present, while transform feedback is active the <parameter>mode</parameter> parameter to\r |
| 57 | <citerefentry><refentrytitle>glDrawArrays</refentrytitle></citerefentry> must match those specified\r |
| 58 | in the following table:\r |
| 59 | </para>\r |
| 60 | <informaltable frame="topbot">\r |
| 61 | <tgroup cols="2" align="left">\r |
| 62 | <colspec colwidth="1.1*" />\r |
| 63 | <colspec colwidth="1*" />\r |
| 64 | <thead>\r |
| 65 | <row>\r |
| 66 | <entry rowsep="1" align="left"><emphasis role="bold">\r |
| 67 | Transform Feedback <parameter>primitiveMode</parameter>\r |
| 68 | </emphasis></entry>\r |
| 69 | <entry rowsep="1" align="left"><emphasis role="bold">\r |
| 70 | Allowed Render Primitive <parameter>modes</parameter>\r |
| 71 | </emphasis></entry>\r |
| 72 | </row>\r |
| 73 | </thead>\r |
| 74 | <tbody>\r |
| 75 | <row>\r |
| 76 | <entry align="left">\r |
| 77 | <constant>GL_POINTS</constant>\r |
| 78 | </entry>\r |
| 79 | <entry align="left">\r |
| 80 | <constant>GL_POINTS</constant>\r |
| 81 | </entry>\r |
| 82 | </row>\r |
| 83 | <row>\r |
| 84 | <entry align="left">\r |
| 85 | <constant>GL_LINES</constant>\r |
| 86 | </entry>\r |
| 87 | <entry align="left">\r |
| 88 | <constant>GL_LINES</constant>, <constant>GL_LINE_LOOP</constant>, <constant>GL_LINE_STRIP</constant>,\r |
| 89 | <constant>GL_LINES_ADJACENCY</constant>, <constant>GL_LINE_STRIP_ADJACENCY</constant>\r |
| 90 | </entry>\r |
| 91 | </row>\r |
| 92 | <row>\r |
| 93 | <entry align="left">\r |
| 94 | <constant>GL_TRIANGLES</constant>\r |
| 95 | </entry>\r |
| 96 | <entry align="left">\r |
| 97 | <constant>GL_TRIANGLES</constant>, <constant>GL_TRIANGLE_STRIP</constant>, <constant>GL_TRIANGLE_FAN</constant>,\r |
| 98 | <constant>GL_TRIANGLES_ADJACENCY</constant>, <constant>GL_TRIANGLE_STRIP_ADJACENCY</constant>\r |
| 99 | </entry>\r |
| 100 | </row>\r |
| 101 | </tbody>\r |
| 102 | </tgroup>\r |
| 103 | </informaltable>\r |
| 104 | <para>\r |
| 105 | If a geometry shader is present, the output primitive type from the geometry shader must match those\r |
| 106 | provided in the following table:\r |
| 107 | <informaltable frame="topbot">\r |
| 108 | <tgroup cols="2" align="left">\r |
| 109 | <colspec colwidth="1.1*" />\r |
| 110 | <colspec colwidth="1*" />\r |
| 111 | <thead>\r |
| 112 | <row>\r |
| 113 | <entry rowsep="1" align="left"><emphasis role="bold">\r |
| 114 | Transform Feedback <parameter>primitiveMode</parameter>\r |
| 115 | </emphasis></entry>\r |
| 116 | <entry rowsep="1" align="left"><emphasis role="bold">\r |
| 117 | Allowed Geometry Shader Output Primitive Type\r |
| 118 | </emphasis></entry>\r |
| 119 | </row>\r |
| 120 | </thead>\r |
| 121 | <tbody>\r |
| 122 | <row>\r |
| 123 | <entry align="left">\r |
| 124 | <constant>GL_POINTS</constant>\r |
| 125 | </entry>\r |
| 126 | <entry align="left">\r |
| 127 | <constant>points</constant>\r |
| 128 | </entry>\r |
| 129 | </row>\r |
| 130 | <row>\r |
| 131 | <entry align="left">\r |
| 132 | <constant>GL_LINES</constant>\r |
| 133 | </entry>\r |
| 134 | <entry align="left">\r |
| 135 | <constant>line_strip</constant>\r |
| 136 | </entry>\r |
| 137 | </row>\r |
| 138 | <row>\r |
| 139 | <entry align="left">\r |
| 140 | <constant>GL_TRIANGLES</constant>\r |
| 141 | </entry>\r |
| 142 | <entry align="left">\r |
| 143 | <constant>triangle_strip</constant>\r |
| 144 | </entry>\r |
| 145 | </row>\r |
| 146 | </tbody>\r |
| 147 | </tgroup>\r |
| 148 | </informaltable>\r |
| 149 | </para>\r |
| 150 | </refsect1>\r |
| 151 | <refsect1 id="notes"><title>Notes</title>\r |
| 152 | <para>\r |
| 153 | Geometry shaders, and the <constant>GL_TRIANGLES_ADJACENCY</constant>, <constant>GL_TRIANGLE_STRIP_ADJACENCY</constant>,\r |
| 154 | <constant>GL_LINES_ADJACENCY</constant> and <constant>GL_LINE_STRIP_ADJACENCY</constant> primtive modes are available\r |
| 155 | only if the GL version is 3.2 or greater.\r |
| 156 | </para>\r |
| 157 | </refsect1>\r |
| 158 | <refsect1 id="errors"><title>Errors</title>\r |
| 159 | <para>\r |
| 160 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBeginTransformFeedback</function> is executed\r |
| 161 | while transform feedback is active.\r |
| 162 | </para>\r |
| 163 | <para>\r |
| 164 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glEndTransformFeedback</function> is executed\r |
| 165 | while transform feedback is not active.\r |
| 166 | </para>\r |
| 167 | <para>\r |
| 168 | <constant>GL_INVALID_OPERATION</constant> is generated by <citerefentry><refentrytitle>glDrawArrays</refentrytitle></citerefentry>\r |
| 169 | if no geometry shader is present, transform feedback is active and <parameter>mode</parameter> is not one of the allowed modes.\r |
| 170 | </para>\r |
| 171 | <para>\r |
| 172 | <constant>GL_INVALID_OPERATION</constant> is generated by <citerefentry><refentrytitle>glDrawArrays</refentrytitle></citerefentry>\r |
| 173 | if a geometry shader is present, transform feedback is active and the output primitive type of the geometry shader does not\r |
| 174 | match the transform feedback <parameter>primitiveMode</parameter>.\r |
| 175 | </para>\r |
| 176 | <para>\r |
| 177 | <constant>GL_INVALID_OPERATION</constant> is generated by <function>glEndTransformFeedback</function> if any binding\r |
| 178 | point used in transform feedback mode does not have a buffer object bound.\r |
| 179 | </para>\r |
| 180 | <para>\r |
| 181 | <constant>GL_INVALID_OPERATION</constant> is generated by <function>glEndTransformFeedback</function> if no binding\r |
| 182 | points would be used, either because no program object is active of because the active program object has specified\r |
| 183 | no varying variables to record.\r |
| 184 | </para>\r |
| 185 | </refsect1>\r |
| 186 | <refsect1 id="Copyright"><title>Copyright</title>\r |
| 187 | <para>\r |
| 188 | Copyright <trademark class="copyright"></trademark> 2010 Khronos Group. \r |
| 189 | This material may be distributed subject to the terms and conditions set forth in \r |
| 190 | the Open Publication License, v 1.0, 8 June 1999.\r |
| 191 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r |
| 192 | </para>\r |
| 193 | </refsect1>\r |
| 194 | </refentry>\r |