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