glMultiDrawElementsIndirect — render indexed primitives from array data, taking parameters from memory
void glMultiDrawElementsIndirect(
|
GLenum mode, |
| GLenum type, | |
| const void *indirect, | |
| GLsizei drawcount, | |
GLsizei stride); |
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.
type
Specifies the type of data in the buffer bound to the GL_ELEMENT_ARRAY_BUFFER binding.
indirect
Specifies the address of a structure containing an array of draw parameters.
drawcount
Specifies the number of elements in the array addressed by indirect.
stride
Specifies the distance in basic machine units between elements of the draw parameter array.
glMultiDrawElementsIndirect specifies multiple indexed geometric primitives
with very few subroutine calls. glMultiDrawElementsIndirect behaves
similarly to a multitude of calls to glDrawElementsInstancedBaseVertexBaseInstance,
execpt that the parameters to glDrawElementsInstancedBaseVertexBaseInstance
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 a structure
that takes the form (in C):
typedef struct {
uint count;
uint instanceCount;
uint firstIndex;
int baseVertex;
uint baseInstance;
} DrawElementsIndirectCommand;
A single call to glMultiDrawElementsIndirect is equivalent, assuming no errors
are generated to:
GLsizei n;
for (n = 0; n < drawcount; n++) {
const DrawElementsIndirectCommand *cmd;
if (stride != 0) {
cmd = (const DrawElementsIndirectCommand *)((uintptr)indirect + n * stride);
} else {
cmd = (const DrawElementsIndirectCommand *)indirect + n;
}
glDrawElementsInstancedBaseVertexBaseInstance(mode,
cmd->count,
type,
cmd->firstIndex * size-of-type,
cmd->instanceCount,
cmd->baseVertex,
cmd->baseInstance);
}
If a buffer is bound to the GL_DRAW_INDIRECT_BUFFER binding at the time
of a call to glDrawElementsIndirect, 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.
Note that indices stored in client memory are not supported. If no buffer is bound to the
GL_ELEMENT_ARRAY_BUFFER binding, an error will be generated.
The results of the operation are undefined if the reservedMustBeZero member
of the parameter structure is non-zero. However, no error is generated in this case.
Vertex attributes that are modified by glDrawElementsIndirect have an
unspecified value after glDrawElementsIndirect returns. Attributes that aren't
modified remain well defined.
The baseInstance member of the DrawElementsIndirectCommand
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.
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 no buffer is bound to the GL_ELEMENT_ARRAY_BUFFER
binding, or if such a buffer's data store is currently mapped.
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.
| OpenGL Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
glMultiDrawElementsIndirect
|
- | - | - | - | - | - | - | - | - | ✔ | ✔ | ✔ |
glDrawArrays, glDrawArraysInstanced, glDrawArraysIndirect, glDrawElements, glDrawRangeElements, glDrawElementsIndirect, glMultiDrawArraysIndirect
Copyright © 2010-2014 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. https://opencontent.org/openpub/.