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 glDrawElementsInstancedBaseVertexBaseInstance,
execpt that the parameters to glDrawElementsInstancedBaseVertexBaseInstance
are stored in memory at the address given by indirect
.
The parameters addressed by indirect
are packed into a structure
that takes the form (in C):
typedef struct { uint count; uint primCount; uint firstIndex; uint baseVertex; uint baseInstance; } DrawElementsIndirectCommand;
glDrawElementsIndirect
is equivalent to:
void glDrawElementsIndirect(GLenum mode, GLenum type, const void * indirect) { const DrawElementsIndirectCommand *cmd = (const DrawElementsIndirectCommand *)indirect; glDrawElementsInstancedBaseVertexBaseInstance(mode, cmd->count, type, cmd->firstIndex + size-of-type, cmd->primCount, 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_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.
glDrawArrays, glDrawArraysInstanced, glDrawArraysIndirect, glDrawElements, glDrawRangeElements,
Copyright © 2010 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/.