libcogl-doc 1.22.2-2 / usr / share / gtk-doc / html / cogl-2.0-experimental / cogl-2.0-experimental-Indices.html

This file is indexed.

/usr/share/gtk-doc/html/cogl-2.0-experimental/cogl-2.0-experimental-Indices.html is in libcogl-doc 1.22.2-2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below. 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Indices: Cogl 2.0 Reference Manual</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="index.html" title="Cogl 2.0 Reference Manual">
<link rel="up" href="cogl-buffer-layout-apis.html" title="Describing the layout of GPU Memory">
<link rel="prev" href="cogl-2.0-experimental-Vertex-Attributes.html" title="Vertex Attributes">
<link rel="next" href="cogl-primitive-apis.html" title="Geometry">
<meta name="generator" content="GTK-Doc V1.25 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle">
<td width="100%" align="left" class="shortcuts">
<a href="#" class="shortcut">Top</a><span id="nav_description">  <span class="dim">|</span> 
                  <a href="#cogl-2.0-experimental-Indices.description" class="shortcut">Description</a></span>
</td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<td><a accesskey="u" href="cogl-buffer-layout-apis.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td>
<td><a accesskey="p" href="cogl-2.0-experimental-Vertex-Attributes.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="n" href="cogl-primitive-apis.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="refentry">
<a name="cogl-2.0-experimental-Indices"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="cogl-2.0-experimental-Indices.top_of_page"></a>Indices</span></h2>
<p>Indices — Describe vertex indices stored in a <a class="link" href="cogl-2.0-experimental-CoglIndexBuffer---Buffers-of-vertex-indices.html#CoglIndexBuffer" title="CoglIndexBuffer"><span class="type">CoglIndexBuffer</span></a>.</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Indices.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Indices.html#cogl-is-indices" title="cogl_is_indices ()">cogl_is_indices</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="returnvalue">CoglIndices</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Indices.html#cogl-indices-new" title="cogl_indices_new ()">cogl_indices_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="returnvalue">CoglIndices</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Indices.html#cogl-get-rectangle-indices" title="cogl_get_rectangle_indices ()">cogl_get_rectangle_indices</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Indices.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices">CoglIndices</a></td>
</tr>
<tr>
<td class="datatype_keyword">enum</td>
<td class="function_name"><a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndicesType" title="enum CoglIndicesType">CoglIndicesType</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Indices.description"></a><h2>Description</h2>
<p>Indices allow you to avoid duplicating vertices in your vertex data
by virtualizing your data and instead providing a sequence of index
values that tell the GPU which data should be used for each vertex.</p>
<p>If the GPU is given a sequence of indices it doesn't simply walk
through each vertex of your data in order it will instead walk
through the indices which can provide random access to the
underlying data.</p>
<p>Since it's very common to have duplicate vertices when describing a
shape as a list of triangles it can often be a significant space
saving to describe geometry using indices. Reducing the size of
your models can make it cheaper to map them into the GPU by
reducing the demand on memory bandwidth and may help to make better
use of your GPUs internal vertex caching.</p>
<p>For example, to describe a quadrilateral as 2 triangles for the GPU
you could either provide data with 6 vertices or instead with
indices you can provide vertex data for just 4 vertices and an
index buffer that specfies the 6 vertices by indexing the shared
vertices multiple times.</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8</pre></td>
        <td class="listing_code"><pre class="programlisting">CoglVertex2f quad_vertices<span class="gtkdoc opt">[] = {</span>
  <span class="gtkdoc opt">{</span>x0<span class="gtkdoc opt">,</span> y0<span class="gtkdoc opt">},</span> <span class="gtkdoc slc">//0 = top left</span>
  <span class="gtkdoc opt">{</span>x1<span class="gtkdoc opt">,</span> y1<span class="gtkdoc opt">},</span> <span class="gtkdoc slc">//1 = bottom left</span>
  <span class="gtkdoc opt">{</span>x2<span class="gtkdoc opt">,</span> y2<span class="gtkdoc opt">},</span> <span class="gtkdoc slc">//2 = bottom right</span>
  <span class="gtkdoc opt">{</span>x3<span class="gtkdoc opt">,</span> y3<span class="gtkdoc opt">},</span> <span class="gtkdoc slc">//3 = top right</span>
<span class="gtkdoc opt">};</span>
<span class="gtkdoc slc">//tell the gpu how to interpret the quad as 2 triangles...</span>
<span class="gtkdoc kwb">unsigned char</span> indices<span class="gtkdoc opt">[] = {</span><span class="number">0</span><span class="gtkdoc opt">,</span> <span class="number">1</span><span class="gtkdoc opt">,</span> <span class="number">2</span><span class="gtkdoc opt">,</span> <span class="number">0</span><span class="gtkdoc opt">,</span> <span class="number">2</span><span class="gtkdoc opt">,</span> <span class="number">3</span><span class="gtkdoc opt">};</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>Even in the above illustration we see a saving of 10bytes for one
quad compared to having data for 6 vertices and no indices but if
you need to draw 100s or 1000s of quads then its really quite
significant.</p>
<p>Something else to consider is that often indices can be defined
once and remain static while the vertex data may change for
animations perhaps. That means you may be able to ignore the
negligable cost of mapping your indices into the GPU if they don't
ever change.</p>
<p>The above illustration is actually a good example of static indices
because it's really common that developers have quad mesh data that
they need to display and we know exactly what that indices array
needs to look like depending on the number of quads that need to be
drawn. It doesn't matter how the quads might be animated and
changed the indices will remain the same. Cogl even has a utility
(<a class="link" href="cogl-2.0-experimental-Indices.html#cogl-get-rectangle-indices" title="cogl_get_rectangle_indices ()"><code class="function">cogl_get_rectangle_indices()</code></a>) to get access to re-useable indices
for drawing quads as above.</p>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Indices.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="cogl-is-indices"></a><h3>cogl_is_indices ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_is_indices (<em class="parameter"><code><span class="type">void</span> *object</code></em>);</pre>
<p>Gets whether the given object references a <a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="type">CoglIndices</span></a>.</p>
<div class="refsect3">
<a name="cogl-is-indices.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>object</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-The-Object-Interface.html#CoglObject" title="CoglObject"><span class="type">CoglObject</span></a> pointer</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="cogl-is-indices.returns"></a><h4>Returns</h4>
<p> <code class="literal">TRUE</code> if the object references a <a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="type">CoglIndices</span></a>
and <code class="literal">FALSE</code> otherwise.</p>
</div>
<p class="since">Since: 1.10</p>
<p class="stability">Stability Level: <acronym title="Unstable interfaces are experimental or transitional. They are typically used to
give outside developers early access to new or rapidly changing technology, or
to provide an interim solution to a problem where a more general solution is
anticipated. No claims are made about either source or binary compatibility from
one minor release to the next.

The Unstable interface level is a warning that these interfaces are  subject to
change without warning and should not be used in unbundled products.

Given such caveats, customer impact need not be a factor when considering
incompatible changes to an Unstable interface in a major or minor release.
Nonetheless, when such changes are introduced, the changes should still be
mentioned in the release notes for the affected release.
"><span class="acronym">Unstable</span></acronym></p>
</div>
<hr>
<div class="refsect2">
<a name="cogl-indices-new"></a><h3>cogl_indices_new ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="returnvalue">CoglIndices</span></a> *
cogl_indices_new (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#CoglContext" title="CoglContext"><span class="type">CoglContext</span></a> *context</code></em>,
                  <em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndicesType" title="enum CoglIndicesType"><span class="type">CoglIndicesType</span></a> type</code></em>,
                  <em class="parameter"><code>const <span class="type">void</span> *indices_data</code></em>,
                  <em class="parameter"><code><span class="type">int</span> n_indices</code></em>);</pre>
</div>
<hr>
<div class="refsect2">
<a name="cogl-get-rectangle-indices"></a><h3>cogl_get_rectangle_indices ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Indices.html#CoglIndices" title="CoglIndices"><span class="returnvalue">CoglIndices</span></a> *
cogl_get_rectangle_indices (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#CoglContext" title="CoglContext"><span class="type">CoglContext</span></a> *context</code></em>,
                            <em class="parameter"><code><span class="type">int</span> n_rectangles</code></em>);</pre>
</div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Indices.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="CoglIndices"></a><h3>CoglIndices</h3>
<pre class="programlisting">typedef struct _CoglIndices CoglIndices;</pre>
</div>
<hr>
<div class="refsect2">
<a name="CoglIndicesType"></a><h3>enum CoglIndicesType</h3>
<p>You should aim to use the smallest data type that gives you enough
range, since it reduces the size of your index array and can help
reduce the demand on memory bandwidth.</p>
<p>Note that <a class="link" href="cogl-2.0-experimental-Indices.html#COGL-INDICES-TYPE-UNSIGNED-INT:CAPS"><code class="literal">COGL_INDICES_TYPE_UNSIGNED_INT</code></a> is only supported if the
<a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#COGL-FEATURE-ID-UNSIGNED-INT-INDICES:CAPS"><code class="literal">COGL_FEATURE_ID_UNSIGNED_INT_INDICES</code></a> feature is available. This
should always be available on OpenGL but on OpenGL ES it will only
be available if the GL_OES_element_index_uint extension is
advertized.</p>
<div class="refsect3">
<a name="CoglIndicesType.members"></a><h4>Members</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>
<tbody>
<tr>
<td class="enum_member_name"><p><a name="COGL-INDICES-TYPE-UNSIGNED-BYTE:CAPS"></a>COGL_INDICES_TYPE_UNSIGNED_BYTE</p></td>
<td class="enum_member_description">
<p>Your indices are unsigned bytes</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="COGL-INDICES-TYPE-UNSIGNED-SHORT:CAPS"></a>COGL_INDICES_TYPE_UNSIGNED_SHORT</p></td>
<td class="enum_member_description">
<p>Your indices are unsigned shorts</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="COGL-INDICES-TYPE-UNSIGNED-INT:CAPS"></a>COGL_INDICES_TYPE_UNSIGNED_INT</p></td>
<td class="enum_member_description">
<p>Your indices are unsigned ints</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
</div>
</div>
<div class="footer">
<hr>Generated by GTK-Doc V1.25</div>
</body>
</html>

APT Browse - Built by Thomas Orozco.