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1 | <?xml version="1.0" encoding="UTF-8"?> |
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4 | <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glProvokingVertex</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="glProvokingVertex"><a id="glProvokingVertex"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glProvokingVertex — specifiy the vertex to be used as the source of data for flat shaded varyings</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glProvokingVertex</b>(</code></td><td>GLenum <var class="pdparam">provokeMode</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>provokeMode</code></em></span></dt><dd><p> | |
5 | Specifies the vertex to be used as the source of data for flat shaded varyings. | |
6 | </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p> | |
7 | <span class="emphasis"><em>Flatshading</em></span> a vertex shader varying output means to assign all vetices of the primitive the same value | |
8 | for that output. The vertex from which these values is derived is known as the <span class="emphasis"><em>provoking vertex</em></span> and | |
9 | <code class="function">glProvokingVertex</code> specifies which vertex is to be used as the source of data for flat shaded varyings. | |
10 | </p><p> | |
11 | <em class="parameter"><code>provokeMode</code></em> must be either <code class="constant">GL_FIRST_VERTEX_CONVENTION</code> or | |
12 | <code class="constant">GL_LAST_VERTEX_CONVENTION</code>, and controls the selection of the vertex whose values are assigned to flatshaded | |
13 | varying outputs. The interpretation of these values for the supported primitive types is: | |
14 | </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /></colgroup><thead><tr><th align="left"><span class="bold"><strong> | |
15 | Primitive Type of Polygon <span class="emphasis"><em>i</em></span> | |
16 | </strong></span></th><th align="left"><span class="bold"><strong> | |
17 | First Vertex Convention | |
18 | </strong></span></th><th align="left"><span class="bold"><strong> | |
19 | Last Vertex Convention | |
20 | </strong></span></th></tr><tr><th align="left"> | |
21 | point | |
22 | </th><th align="left"> | |
23 | <span class="emphasis"><em>i</em></span> | |
24 | </th><th align="left"> | |
25 | <span class="emphasis"><em>i</em></span> | |
26 | </th></tr><tr><th align="left"> | |
27 | independent line | |
28 | </th><th align="left"> | |
29 | 2<span class="emphasis"><em>i</em></span> - 1 | |
30 | </th><th align="left"> | |
31 | 2<span class="emphasis"><em>i</em></span> | |
32 | </th></tr><tr><th align="left"> | |
33 | line loop | |
34 | </th><th align="left"> | |
35 | <span class="emphasis"><em>i</em></span> | |
36 | </th><th align="left"> | |
37 | <p> | |
38 | <span class="emphasis"><em>i</em></span> + 1, if <span class="emphasis"><em>i</em></span> < <span class="emphasis"><em>n</em></span> | |
39 | </p> | |
40 | <p> | |
41 | 1, if <span class="emphasis"><em>i</em></span> = <span class="emphasis"><em>n</em></span> | |
42 | </p> | |
43 | </th></tr><tr><th align="left"> | |
44 | line strip | |
45 | </th><th align="left"> | |
46 | <span class="emphasis"><em>i</em></span> | |
47 | </th><th align="left"> | |
48 | <span class="emphasis"><em>i</em></span> + 1 | |
49 | </th></tr><tr><th align="left"> | |
50 | independent triangle | |
51 | </th><th align="left"> | |
52 | 3<span class="emphasis"><em>i</em></span> - 2 | |
53 | </th><th align="left"> | |
54 | 3<span class="emphasis"><em>i</em></span> | |
55 | </th></tr><tr><th align="left"> | |
56 | triangle strip | |
57 | </th><th align="left"> | |
58 | <span class="emphasis"><em>i</em></span> | |
59 | </th><th align="left"> | |
60 | <span class="emphasis"><em>i</em></span> + 2 | |
61 | </th></tr><tr><th align="left"> | |
62 | triangle fan | |
63 | </th><th align="left"> | |
64 | <span class="emphasis"><em>i</em></span> + 1 | |
65 | </th><th align="left"> | |
66 | <span class="emphasis"><em>i</em></span> + 2 | |
67 | </th></tr><tr><th align="left"> | |
68 | line adjacency | |
69 | </th><th align="left"> | |
70 | 4<span class="emphasis"><em>i</em></span> - 2 | |
71 | </th><th align="left"> | |
72 | 4<span class="emphasis"><em>i</em></span> - 1 | |
73 | </th></tr><tr><th align="left"> | |
74 | line strip adjacency | |
75 | </th><th align="left"> | |
76 | <span class="emphasis"><em>i</em></span> + 1 | |
77 | </th><th align="left"> | |
78 | <span class="emphasis"><em>i</em></span> + 2 | |
79 | </th></tr><tr><th align="left"> | |
80 | triangle adjacency | |
81 | </th><th align="left"> | |
82 | 6<span class="emphasis"><em>i</em></span> - 5 | |
83 | </th><th align="left"> | |
84 | 6<span class="emphasis"><em>i</em></span> - 1 | |
85 | </th></tr><tr><th align="left"> | |
86 | triangle strip adjacency | |
87 | </th><th align="left"> | |
88 | 2<span class="emphasis"><em>i</em></span> - 1 | |
89 | </th><th align="left"> | |
90 | 2<span class="emphasis"><em>i</em></span> + 3 | |
91 | </th></tr></thead></table></div><p> | |
92 | </p><p> | |
93 | If a vertex or geometry shader is active, user-defined varying outputs may be flatshaded by using the | |
94 | <code class="code">flat</code> qualifier when declaring the output. | |
95 | </p></div><div class="refsect1" title="Notes"><a id="notes"></a><h2>Notes</h2><p> | |
96 | <code class="function">glProvokingVertex</code> is available only if the GL version is 3.2 or greater. | |
97 | </p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p> | |
98 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>provokeMode</code></em> is not an accepted value. | |
99 | </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p> | |
100 | Copyright <span class="trademark"></span>© 2010 Khronos Group. | |
101 | This material may be distributed subject to the terms and conditions set forth in | |
102 | the Open Publication License, v 1.0, 8 June 1999. | |
103 | <a class="ulink" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
104 | </p></div></div></body></html> |