glDrawElementsIndirect — render indexed primitives from array data, taking parameters from memory
void glDrawElementsIndirect(
|
GLenum mode, |
GLenum type, | |
const void *indirect) ; |
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 the draw parameters.
glDrawElementsIndirect
specifies multiple indexed geometric primitives
with very few subroutine calls. glDrawElementsIndirect
behaves
similarly to glDrawElementsInstanced,
except that the parameters to glDrawElementsInstanced
are stored in memory at the address given by indirect
and the ith element
transferred by the corresponding draw call will be taken from element indices
[i] + baseVertex
of each enabled array. If the resulting value is larger than the maximum value representable by type
,
it is as if the calculation were upconverted to 32-bit unsigned integers (with wrapping on overflow conditions).
The operation is undefined if the sum would be negative.It also supports the addition of
a value baseVertex to each index.
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 reservedMustBeZero; } DrawElementsIndirectCommand;
glDrawElementsIndirect
is equivalent to:
void glDrawElementsIndirect(GLenum mode, GLenum type, const void * indirect) { const DrawElementsIndirectCommand *cmd = (const DrawElementsIndirectCommand *)indirect; glDrawElementsInstancedBaseVertex(mode, cmd->count, type, cmd->firstIndex * size-of-type, cmd->instanceCount, cmd->baseVertex); }
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.
glDrawElementsInstancedBaseVertex
isn't actually present in OpenGL ES, but is used to describe this functionality.
GL_LINE_STRIP_ADJACENCY
,
GL_LINES_ADJACENCY
,
GL_TRIANGLE_STRIP_ADJACENCY
,
GL_TRIANGLES_ADJACENCY
and
GL_PATCHES
are available only if the GL ES version is 3.2 or greater.
GL_INVALID_ENUM
is generated if
mode
is not an accepted value.
GL_INVALID_OPERATION
is generated if zero
is bound to the GL_VERTEX_ARRAY_BINDING
,
GL_DRAW_INDIRECT_BUFFER
, or
GL_ELEMENT_ARRAY_BUFFER
binding, or to any
enabled vertex array.
GL_INVALID_OPERATION
is generated if the
command would source data beyond the end of any bound buffer
object.
GL_INVALID_VALUE
is generated if
indirect
is not a multiple of the size,
in basic machine units, of GLuint
.
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.
OpenGL ES API Version | ||||
---|---|---|---|---|
Function Name | 2.0 | 3.0 | 3.1 | 3.2 |
glDrawElementsIndirect
|
- | - | ✔ | ✔ |
glDrawArrays, glDrawArraysInstanced, glDrawArraysIndirect, glDrawElements, glDrawRangeElements,
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