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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=
"glDrawElementsInstancedBaseVertexBaseInstance"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>glDrawElementsInstancedBaseVertexBaseInstance — render multiple instances of a set of primitives from array data with a per-element offset
</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">glDrawElementsInstancedBaseVertexBaseInstance
</b>(
</code></td><td>GLenum
</td><td><var class=
"pdparam">mode
</var>,
</td></tr><tr><td> </td><td>GLsizei
</td><td><var class=
"pdparam">count
</var>,
</td></tr><tr><td> </td><td>GLenum
</td><td><var class=
"pdparam">type
</var>,
</td></tr><tr><td> </td><td>GLvoid *
</td><td><var class=
"pdparam">indices
</var>,
</td></tr><tr><td> </td><td>GLsizei
</td><td><var class=
"pdparam">primcount
</var>,
</td></tr><tr><td> </td><td>GLint
</td><td><var class=
"pdparam">basevertex
</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.
7 <code class=
"constant">GL_POINTS
</code>,
<code class=
"constant">GL_LINE_STRIP
</code>,
<code class=
"constant">GL_LINE_LOOP
</code>,
8 <code class=
"constant">GL_LINES
</code>,
<code class=
"constant">GL_TRIANGLE_STRIP
</code>,
<code class=
"constant">GL_TRIANGLE_FAN
</code>,
9 <code class=
"constant">GL_TRIANGLES
</code>,
<code class=
"constant">GL_LINES_ADJACENCY
</code>,
<code class=
"constant">GL_LINE_STRIP_ADJACENCY
</code>,
10 <code class=
"constant">GL_TRIANGLES_ADJACENCY
</code>,
<code class=
"constant">GL_TRIANGLE_STRIP_ADJACENCY
</code> and
<code class=
"constant">GL_PATCHES
</code> are accepted.
11 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>count
</code></em></span></dt><dd><p>
12 Specifies the number of elements to be rendered.
13 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>type
</code></em></span></dt><dd><p>
14 Specifies the type of the values in indices. Must be one of
<code class=
"constant">GL_UNSIGNED_BYTE
</code>,
15 <code class=
"constant">GL_UNSIGNED_SHORT
</code>, or
<code class=
"constant">GL_UNSIGNED_INT
</code>.
16 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>indices
</code></em></span></dt><dd><p>
17 Specifies a pointer to the location where the indices are stored.
18 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>primcount
</code></em></span></dt><dd><p>
19 Specifies the number of instances of the indexed geometry that should be drawn.
20 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>basevertex
</code></em></span></dt><dd><p>
21 Specifies a constant that should be added to each element of
<em class=
"parameter"><code>indices
</code></em>
22 when chosing elements from the enabled vertex arrays.
23 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>baseinstance
</code></em></span></dt><dd><p>
24 Specifies the base instance for use in fetching instanced vertex attributes.
25 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
26 <code class=
"function">glDrawElementsInstancedBaseVertexBaseInstance
</code> behaves identically to
27 <a href=
"glDrawElementsInstanced.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawElementsInstanced
</span></span></a> except that the
<span class=
"emphasis"><em>i
</em></span>th element
28 transferred by the corresponding draw call will be taken from element
<em class=
"parameter"><code>indices
</code></em>[i] +
<em class=
"parameter"><code>basevertex
</code></em>
29 of each enabled array. If the resulting value is larger than the maximum value representable by
<em class=
"parameter"><code>type
</code></em>,
30 it is as if the calculation were upconverted to
32-bit unsigned integers (with wrapping on overflow conditions).
31 The operation is undefined if the sum would be negative. The
<em class=
"parameter"><code>basevertex
</code></em> has no effect on the
32 shader-visible value of
<code class=
"constant">gl_VertexID
</code>.
34 Specific vertex attributes may be classified as
<span class=
"emphasis"><em>instanced
</em></span> through the use of
35 <a href=
"glVertexAttribDivisor.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glVertexAttribDivisor
</span></span></a>. Instanced vertex attributes
36 supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex
37 attribute arrays is calculated as
38 <mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
40 <mml:mfenced open=
"⌊" close=
"⌋">
45 <mml:mi>InstanceID
</mml:mi>
47 <mml:mi>divisor
</mml:mi>
50 <mml:mo lspace=
"2px" rspace=
"2px">+
</mml:mo>
51 <mml:mi>baseInstance
</mml:mi>
53 </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>.
54 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"notes"></a><h2>Notes
</h2><code class=
"function">glDrawElementsInstancedBaseVertex
</code> is only supported if the GL version is
3.2 or greater.
55 </div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"errors"></a><h2>Errors
</h2><p>
56 <code class=
"constant">GL_INVALID_ENUM
</code> is generated if
<em class=
"parameter"><code>mode
</code></em> is not an accepted value.
58 <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> is negative.
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.
63 <code class=
"constant">GL_INVALID_OPERATION
</code> is generated if a non-zero buffer object name is bound to an
64 enabled array or the element array and the buffer object's data store is currently mapped.
65 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"seealso"></a><h2>See Also
</h2><p>
66 <a href=
"glDrawElements.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawElements
</span></span></a>,
67 <a href=
"glDrawRangeElements.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawRangeElements
</span></span></a>,
68 <a href=
"glDrawRangeElementsBaseVertex.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawRangeElementsBaseVertex
</span></span></a>,
69 <a href=
"glDrawElementsInstanced.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawElementsInstanced
</span></span></a>,
70 <a href=
"glDrawElementsInstancedBaseVertex.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDrawElementsInstancedBaseVertex
</span></span></a>
71 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
72 Copyright
<span class=
"trademark"></span>©
2011 Khronos Group.
73 This material may be distributed subject to the terms and conditions set forth in
74 the Open Publication License, v
1.0,
8 June
1999.
75 <a href=
"http://opencontent.org/openpub/" target=
"_top">http://opencontent.org/openpub/
</a>.
76 </p></div></div></body></html>