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=
"glDrawElementsInstancedBaseVertexBaseInstance">
9 <holder>Khronos Group
</holder>
12 <refentrytitle>glDrawElementsInstancedBaseVertexBaseInstance
</refentrytitle>
13 <manvolnum>3G
</manvolnum>
16 <refname>glDrawElementsInstancedBaseVertexBaseInstance
</refname>
17 <refpurpose>render multiple instances of a set of primitives from array data with a per-element offset
</refpurpose>
19 <refsynopsisdiv><title>C Specification
</title>
22 <funcdef>void
<function>glDrawElementsInstancedBaseVertexBaseInstance
</function></funcdef>
23 <paramdef>GLenum
<parameter>mode
</parameter></paramdef>
24 <paramdef>GLsizei
<parameter>count
</parameter></paramdef>
25 <paramdef>GLenum
<parameter>type
</parameter></paramdef>
26 <paramdef>GLvoid *
<parameter>indices
</parameter></paramdef>
27 <paramdef>GLsizei
<parameter>primcount
</parameter></paramdef>
28 <paramdef>GLint
<parameter>basevertex
</parameter></paramdef>
29 <paramdef>GLuint
<parameter>baseinstance
</parameter></paramdef>
33 <!-- eqn: ignoring delim $$ -->
34 <refsect1 id=
"parameters"><title>Parameters
</title>
37 <term><parameter>mode
</parameter></term>
40 Specifies what kind of primitives to render.
42 <constant>GL_POINTS
</constant>,
<constant>GL_LINE_STRIP
</constant>,
<constant>GL_LINE_LOOP
</constant>,
43 <constant>GL_LINES
</constant>,
<constant>GL_TRIANGLE_STRIP
</constant>,
<constant>GL_TRIANGLE_FAN
</constant>,
44 <constant>GL_TRIANGLES
</constant>,
<constant>GL_LINES_ADJACENCY
</constant>,
<constant>GL_LINE_STRIP_ADJACENCY
</constant>,
45 <constant>GL_TRIANGLES_ADJACENCY
</constant>,
<constant>GL_TRIANGLE_STRIP_ADJACENCY
</constant> and
<constant>GL_PATCHES
</constant> are accepted.
50 <term><parameter>count
</parameter></term>
53 Specifies the number of elements to be rendered.
58 <term><parameter>type
</parameter></term>
61 Specifies the type of the values in indices. Must be one of
<constant>GL_UNSIGNED_BYTE
</constant>,
62 <constant>GL_UNSIGNED_SHORT
</constant>, or
<constant>GL_UNSIGNED_INT
</constant>.
67 <term><parameter>indices
</parameter></term>
70 Specifies a pointer to the location where the indices are stored.
75 <term><parameter>primcount
</parameter></term>
78 Specifies the number of instances of the indexed geometry that should be drawn.
83 <term><parameter>basevertex
</parameter></term>
86 Specifies a constant that should be added to each element of
<parameter>indices
</parameter>
87 when chosing elements from the enabled vertex arrays.
92 <term><parameter>baseinstance
</parameter></term>
95 Specifies the base instance for use in fetching instanced vertex attributes.
101 <refsect1 id=
"description"><title>Description
</title>
103 <function>glDrawElementsInstancedBaseVertexBaseInstance
</function> behaves identically to
104 <citerefentry><refentrytitle>glDrawElementsInstanced
</refentrytitle></citerefentry> except that the
<emphasis>i
</emphasis>th element
105 transferred by the corresponding draw call will be taken from element
<parameter>indices
</parameter>[i] +
<parameter>basevertex
</parameter>
106 of each enabled array. If the resulting value is larger than the maximum value representable by
<parameter>type
</parameter>,
107 it is as if the calculation were upconverted to
32-bit unsigned integers (with wrapping on overflow conditions).
108 The operation is undefined if the sum would be negative. The
<parameter>basevertex
</parameter> has no effect on the
109 shader-visible value of
<constant>gl_VertexID
</constant>.
112 Specific vertex attributes may be classified as
<emphasis>instanced
</emphasis> through the use of
113 <citerefentry><refentrytitle>glVertexAttribDivisor
</refentrytitle></citerefentry>. Instanced vertex attributes
114 supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex
115 attribute arrays is calculated as
118 <mml:mfenced open = '
⌊' close = '
⌋'
>
123 <mml:mi>InstanceID
</mml:mi>
125 <mml:mi>divisor
</mml:mi>
128 <mml:mo lspace='
2px' rspace='
2px'
>+</mml:mo>
129 <mml:mi>baseInstance
</mml:mi>
131 </mml:math>. Note that
<parameter>baseinstance
</parameter> does not affect the shader-visible value of
<constant>gl_InstanceID
</constant>.
134 <refsect1 id=
"notes"><title>Notes
</title>
135 <function>glDrawElementsInstancedBaseVertex
</function> is only supported if the GL version is
3.2 or greater.
137 <refsect1 id=
"errors"><title>Errors
</title>
139 <constant>GL_INVALID_ENUM
</constant> is generated if
<parameter>mode
</parameter> is not an accepted value.
142 <constant>GL_INVALID_VALUE
</constant> is generated if
<parameter>count
</parameter> or
<parameter>primcount
</parameter> is negative.
145 <constant>GL_INVALID_OPERATION
</constant> is generated if a geometry shader is active and
<parameter>mode
</parameter>
146 is incompatible with the input primitive type of the geometry shader in the currently installed program object.
149 <constant>GL_INVALID_OPERATION
</constant> is generated if a non-zero buffer object name is bound to an
150 enabled array or the element array and the buffer object's data store is currently mapped.
153 <refsect1 id=
"seealso"><title>See Also
</title>
155 <citerefentry><refentrytitle>glDrawElements
</refentrytitle></citerefentry>,
156 <citerefentry><refentrytitle>glDrawRangeElements
</refentrytitle></citerefentry>,
157 <citerefentry><refentrytitle>glDrawRangeElementsBaseVertex
</refentrytitle></citerefentry>,
158 <citerefentry><refentrytitle>glDrawElementsInstanced
</refentrytitle></citerefentry>,
159 <citerefentry><refentrytitle>glDrawElementsInstancedBaseVertex
</refentrytitle></citerefentry>
162 <refsect1 id=
"Copyright"><title>Copyright
</title>
164 Copyright
<trademark class=
"copyright"></trademark> 2011 Khronos Group.
165 This material may be distributed subject to the terms and conditions set forth in
166 the Open Publication License, v
1.0,
8 June
1999.
167 <ulink url=
"http://opencontent.org/openpub/">http://opencontent.org/openpub/
</ulink>.