Signature
Parameters
Description
glMultiDrawArraysIndirect
specifies multiple geometric primitives
with very few subroutine calls.
glMultiDrawArraysIndirect
behaves
similarly to a multitude of calls to
glDrawArraysInstancedBaseInstance
,
execept that the parameters to each call to
glDrawArraysInstancedBaseInstance
are stored in an array in memory at the address given by
indirect
, separated
by the stride, in basic machine units, specified by
stride
. If
stride
is zero, then the array is assumed to be tightly packed in memory.
The parameters addressed by
indirect
are packed into an array of structures,
each element of which takes the form (in C):
typedef struct {
uint count;
uint instanceCount;
uint first;
uint baseInstance;
} DrawArraysIndirectCommand;
A single call to
glMultiDrawArraysIndirect
is equivalent, assuming no errors
are generated to:
GLsizei n;
for (n = 0; n < drawcount; n++) {
const DrawArraysIndirectCommand *cmd;
if (stride != 0) {
cmd = (const DrawArraysIndirectCommand *)((uintptr)indirect + n * stride);
} else {
cmd = (const DrawArraysIndirectCommand *)indirect + n;
}
glDrawArraysInstancedBaseInstance(mode, cmd->first, cmd->count, cmd->instanceCount, cmd->baseInstance);
}
If a buffer is bound to the
GL_DRAW_INDIRECT_BUFFER
binding at the time
of a call to
glMultiDrawArraysIndirect
,
indirect
is interpreted as an offset, in basic machine units, into that buffer and the parameter
data is read from the buffer rather than from client memory.
In contrast to
glDrawArraysInstancedBaseInstance
,
the
first
member of the parameter structure is unsigned, and out-of-range indices
do not generate an error.
Vertex attributes that are modified by
glMultiDrawArraysIndirect
have an
unspecified value after
glMultiDrawArraysIndirect
returns. Attributes that aren't
modified remain well defined.
Notes
The
baseInstance
member of the
DrawArraysIndirectCommand
structure is defined only if the GL version is 4.2 or greater. For versions of the GL less than 4.2,
this parameter is present but is reserved and should be set to zero. On earlier versions of the GL,
behavior is undefined if it is non-zero.
glMultiDrawArraysIndirect
is available only if the GL version is 4.3 or greater.
Errors
GL_INVALID_ENUM
is generated if
mode
is not an accepted value.
GL_INVALID_VALUE
is generated if
stride
is not a multiple
of four.
GL_INVALID_VALUE
is generated if
drawcount
is negative.
GL_INVALID_OPERATION
is generated if a non-zero buffer object name is bound to an
enabled array or to the
GL_DRAW_INDIRECT_BUFFER
binding and the buffer object's data store is currently mapped.
GL_INVALID_OPERATION
is generated if a geometry shader is active and
mode
is incompatible with the input primitive type of the geometry shader in the currently installed program object.
GL_INVALID_OPERATION
is generated if
mode
is
GL_PATCHES
and no tessellation control shader is active.
Version Support
| glMultiDrawArraysIndirect |
See Also
Copyright
Copyright
2012-2014 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.
http://opencontent.org/openpub/
.