'\" t
.\"     Title: glDrawElementsInstancedBaseInstance
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets v1.79.2 <http://docbook.sf.net/>
.\"      Date: 10/20/2024
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "GLDRAWELEMENTSINSTAN" "3G" "10/20/2024" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
glDrawElementsInstancedBaseInstance \- draw multiple instances of a set of elements with offset applied to instanced attributes
.SH "C SPECIFICATION"
.HP \w'void\ glDrawElementsInstancedBaseInstance('u
.BI "void glDrawElementsInstancedBaseInstance(GLenum\ " "mode" ", GLsizei\ " "count" ", GLenum\ " "type" ", const\ void\ *\ " "indices" ", GLsizei\ " "instancecount" ", GLuint\ " "baseinstance" ");"
.SH "PARAMETERS"
.PP
\fImode\fR
.RS 4
Specifies what kind of primitives to render\&. Symbolic constants
\fBGL_POINTS\fR,
\fBGL_LINE_STRIP\fR,
\fBGL_LINE_LOOP\fR,
\fBGL_LINES\fR,
\fBGL_LINE_STRIP_ADJACENCY\fR,
\fBGL_LINES_ADJACENCY\fR,
\fBGL_TRIANGLE_STRIP\fR,
\fBGL_TRIANGLE_FAN\fR,
\fBGL_TRIANGLES\fR,
\fBGL_TRIANGLE_STRIP_ADJACENCY\fR,
\fBGL_TRIANGLES_ADJACENCY\fR
and
\fBGL_PATCHES\fR
are accepted\&.
.RE
.PP
\fIcount\fR
.RS 4
Specifies the number of elements to be rendered\&.
.RE
.PP
\fItype\fR
.RS 4
Specifies the type of the values in
\fIindices\fR\&. Must be one of
\fBGL_UNSIGNED_BYTE\fR,
\fBGL_UNSIGNED_SHORT\fR, or
\fBGL_UNSIGNED_INT\fR\&.
.RE
.PP
\fIindices\fR
.RS 4
Specifies a pointer to the location where the indices are stored\&.
.RE
.PP
\fIinstancecount\fR
.RS 4
Specifies the number of instances of the specified range of indices to be rendered\&.
.RE
.PP
\fIbaseinstance\fR
.RS 4
Specifies the base instance for use in fetching instanced vertex attributes\&.
.RE
.SH "DESCRIPTION"
.PP
\fBglDrawElementsInstancedBaseInstance\fR
behaves identically to
\fBglDrawElements\fR()
except that
\fIinstancecount\fR
instances of the set of elements are executed and the value of the internal counter
\fIinstanceID\fR
advances for each iteration\&.
\fIinstanceID\fR
is an internal 32\-bit integer counter that may be read by a vertex shader as
\fBgl_InstanceID\fR\&.
.PP
\fBglDrawElementsInstancedBaseInstance\fR
has the same effect as:
.sp
.if n \{\
.RS 4
.\}
.nf
    if (mode, count, or type is invalid )
        generate appropriate error
    else {
        for (int i = 0; i < instancecount ; i++) {
            instanceID = i;
            glDrawElements(mode, count, type, indices);
        }
        instanceID = 0;
    }
.fi
.if n \{\
.RE
.\}
.PP
Specific vertex attributes may be classified as
\fIinstanced\fR
through the use of
\fBglVertexAttribDivisor\fR()\&. Instanced vertex attributes supply per\-instance vertex data to the vertex shader\&. The index of the vertex fetched from the enabled instanced vertex attribute arrays is calculated as
gl _ InstanceID divisor + baseInstance\&. Note that
\fIbaseinstance\fR
does not affect the shader\-visible value of
\fBgl_InstanceID\fR\&.
.SH "NOTES"
.PP
\fBglDrawElementsInstancedBaseInstance\fR
is available only if the GL version is 4\&.2 or greater\&.
.PP
\fBGL_LINE_STRIP_ADJACENCY\fR,
\fBGL_LINES_ADJACENCY\fR,
\fBGL_TRIANGLE_STRIP_ADJACENCY\fR
and
\fBGL_TRIANGLES_ADJACENCY\fR
are available only if the GL version is 3\&.2 or greater\&.
.SH "ERRORS"
.PP
\fBGL_INVALID_ENUM\fR
is generated if
\fImode\fR
is not one of
\fBGL_POINTS\fR,
\fBGL_LINE_STRIP\fR,
\fBGL_LINE_LOOP\fR,
\fBGL_LINES\fR,
\fBGL_TRIANGLE_STRIP\fR,
\fBGL_TRIANGLE_FAN\fR, or
\fBGL_TRIANGLES\fR\&.
.PP
\fBGL_INVALID_VALUE\fR
is generated if
\fIcount\fR
or
\fIinstancecount\fR
is negative\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if a geometry shader is active and
\fImode\fR
is incompatible with the input primitive type of the geometry shader in the currently installed program object\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if a non\-zero buffer object name is bound to an enabled array and the buffer object\*(Aqs data store is currently mapped\&.
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Version\fR
T}
T{
\fBFunction / Feature Name\fR
T}:T{
\fB2\&.0\fR
T}:T{
\fB2\&.1\fR
T}:T{
\fB3\&.0\fR
T}:T{
\fB3\&.1\fR
T}:T{
\fB3\&.2\fR
T}:T{
\fB3\&.3\fR
T}:T{
\fB4\&.0\fR
T}:T{
\fB4\&.1\fR
T}:T{
\fB4\&.2\fR
T}:T{
\fB4\&.3\fR
T}:T{
\fB4\&.4\fR
T}:T{
\fB4\&.5\fR
T}
.T&
l c c c c c c c c c c c c.
T{
\fBglDrawElementsInstancedBaseInstance\fR
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.PP
\fBglDrawElements\fR(),
\fBglDrawArraysInstanced\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
2011\-2014 Khronos Group\&. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1\&.0, 8 June 1999\&.
\m[blue]\fBhttps://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2011-2014 Khronos Group
.br