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1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> | |
3 | <!-- saved from url=(0013)about:internet --> | |
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>glDrawArraysInstancedBaseInstance - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glDrawArraysInstancedBaseInstance"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glDrawArraysInstancedBaseInstance — draw multiple instances of a range of elements with offset applied to instanced attributes</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glDrawArraysInstancedBaseInstance</b>(</code></td><td>GLenum </td><td><var class="pdparam">mode</var>, </td></tr><tr><td> </td><td>GLint </td><td><var class="pdparam">first</var>, </td></tr><tr><td> </td><td>GLsizei </td><td><var class="pdparam">count</var>, </td></tr><tr><td> </td><td>GLsizei </td><td><var class="pdparam">primcount</var>, </td></tr><tr><td> </td><td>GLuint </td><td><var class="pdparam">baseinstance</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p> | |
5 | Specifies what kind of primitives to render. Symbolic constants <code class="constant">GL_POINTS</code>, | |
6 | <code class="constant">GL_LINE_STRIP</code>, <code class="constant">GL_LINE_LOOP</code>, <code class="constant">GL_LINES</code>, | |
7 | <code class="constant">GL_TRIANGLE_STRIP</code>, <code class="constant">GL_TRIANGLE_FAN</code>, <code class="constant">GL_TRIANGLES</code> | |
8 | <code class="constant">GL_LINES_ADJACENCY</code>, <code class="constant">GL_LINE_STRIP_ADJACENCY</code>, | |
9 | <code class="constant">GL_TRIANGLES_ADJACENCY</code>, <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code> and <code class="constant">GL_PATCHES</code> | |
10 | are accepted. | |
11 | </p></dd><dt><span class="term"><em class="parameter"><code>first</code></em></span></dt><dd><p> | |
12 | Specifies the starting index in the enabled arrays. | |
13 | </p></dd><dt><span class="term"><em class="parameter"><code>count</code></em></span></dt><dd><p> | |
14 | Specifies the number of indices to be rendered. | |
15 | </p></dd><dt><span class="term"><em class="parameter"><code>primcount</code></em></span></dt><dd><p> | |
16 | Specifies the number of instances of the specified range of indices to be rendered. | |
17 | </p></dd><dt><span class="term"><em class="parameter"><code>baseinstance</code></em></span></dt><dd><p> | |
18 | Specifies the base instance for use in fetching instanced vertex attributes. | |
19 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
20 | <code class="function">glDrawArraysInstancedBaseInstance</code> behaves identically to <a href="glDrawArrays.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a> | |
21 | except that <em class="parameter"><code>primcount</code></em> instances of the range of elements are executed and the value of the internal counter | |
22 | <em class="parameter"><code>instanceID</code></em> advances for each iteration. <em class="parameter"><code>instanceID</code></em> is an internal 32-bit integer counter | |
23 | that may be read by a vertex shader as <code class="constant">gl_InstanceID</code>. | |
24 | </p><p> | |
25 | <code class="function">glDrawArraysInstancedBaseInstance</code> has the same effect as: | |
26 | </p><pre class="programlisting"> if ( mode or count is invalid ) | |
27 | generate appropriate error | |
28 | else { | |
29 | for (int i = 0; i < primcount ; i++) { | |
30 | instanceID = i; | |
31 | glDrawArrays(mode, first, count); | |
32 | } | |
33 | instanceID = 0; | |
34 | }</pre><p> | |
35 | </p><p> | |
36 | Specific vertex attributes may be classified as <span class="emphasis"><em>instanced</em></span> through the use of | |
37 | <a href="glVertexAttribDivisor.xml"><span class="citerefentry"><span class="refentrytitle">glVertexAttribDivisor</span></span></a>. Instanced vertex attributes | |
38 | supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex | |
39 | attribute arrays is calculated as: | |
40 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> | |
41 | <mml:mrow> | |
42 | <mml:mfenced open="⌊" close="⌋"> | |
43 | <mml:mfrac> | |
44 | <mml:mrow> | |
45 | <mml:mi>gl</mml:mi> | |
46 | <mml:mo>_</mml:mo> | |
47 | <mml:mi>InstanceID</mml:mi> | |
48 | </mml:mrow> | |
49 | <mml:mi>divisor</mml:mi> | |
50 | </mml:mfrac> | |
51 | </mml:mfenced> | |
52 | <mml:mo lspace="2px" rspace="2px">+</mml:mo> | |
53 | <mml:mi>baseInstance</mml:mi> | |
54 | </mml:mrow> | |
55 | </mml:math>. Note that <em class="parameter"><code>baseinstance</code></em> does not affect the shader-visible value of <code class="constant">gl_InstanceID</code>. | |
56 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
57 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not one of | |
58 | the accepted values. | |
59 | </p><p> | |
60 | <code class="constant">GL_INVALID_OPERATION</code> is generated if a geometry shader is active and <em class="parameter"><code>mode</code></em> | |
61 | is incompatible with the input primitive type of the geometry shader in the currently installed program object. | |
62 | </p><p> | |
63 | <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>count</code></em> or <em class="parameter"><code>primcount</code></em> are negative. | |
64 | </p><p> | |
65 | <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to an | |
66 | enabled array and the buffer object's data store is currently mapped. | |
67 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
68 | <a href="glDrawArrays.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>, | |
69 | <a href="glDrawElementsInstanced.xml"><span class="citerefentry"><span class="refentrytitle">glDrawElementsInstanced</span></span></a> | |
70 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
71 | Copyright <span class="trademark"></span>© 2011 Khronos Group. | |
72 | This material may be distributed subject to the terms and conditions set forth in | |
73 | the Open Publication License, v 1.0, 8 June 1999. | |
74 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
75 | </p></div></div></body></html> |