glMultiDrawArraysIndirect man page on RedHat
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GLMULTIDRAWARRAYSIND(3G) OpenGL Manual GLMULTIDRAWARRAYSIND(3G)
NAME
glMultiDrawArraysIndirect - render multiple sets of primitives from
array data, taking parameters from memory
C SPECIFICATION
void glMultiDrawArraysIndirect(GLenum mode, const void *indirect,
GLsizei drawcount, GLsizei stride);
PARAMETERS
mode
Specifies what kind of primitives to render. Symbolic constants
GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES,
GL_LINE_STRIP_ADJACENCY, GL_LINES_ADJACENCY, GL_TRIANGLE_STRIP,
GL_TRIANGLE_FAN, GL_TRIANGLES, GL_TRIANGLE_STRIP_ADJACENCY,
GL_TRIANGLES_ADJACENCY, and GL_PATCHES are accepted.
indirect
Specifies the address of an array of structures containing the draw
parameters.
drawcount
Specifies the the number of elements in the array of draw parameter
structures.
stride
Specifies the distance in basic machine units between elements of
the draw parameter array.
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 primCount;
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->primCount, 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.
SEE ALSO
glDrawArrays(), glDrawArraysInstanced(), glDrawElements(),
glDrawRangeElements(), glDrawArraysIndirect(),
glMultiDrawElementsIndirect()
COPYRIGHT
Copyright © 2012 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/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLMULTIDRAWARRAYSIND(3G)
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