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Name
ANGLE_multi_draw
Name Strings
GL_ANGLE_multi_draw
Contributors
Austin Eng, Google Inc.
Kai Ninomiya, Google Inc.
Kenneth Russell, Google Inc.
Contributors to the EXT_multi_draw_arrays specification
Contributors to the ARB_shader_draw_parameters specification
Contact
Austin Eng (enga 'at' google.com)
Status
Incomplete
Version
Last Modified Date: October 24, 2018
Author Revision: 1
Number
OpenGL ES Extension XX
Dependencies
OpenGL ES 2.0 is required.
This extension is written against the OpenGL ES 2.0 specification,
the OpenGL ES 3.0 specification, and the OpenGL ES Shading Language 3.0
specification.
The presence of the GL_ANGLE_instanced_arrays or GL_EXT_instanced_arrays
extensions affects the definition of this extension.
Overview
This extension exposes the Multi* draw call variants in
EXT_multi_draw_arrays functionality in addition to the vertex shader builtin
gl_DrawID exposed by ARB_shader_draw_parameters for OpenGL.
These functions behave identically to the standard functions
DrawArrays() and DrawElements() except they handle multiple lists of
vertices in one call. Their main purpose is to allow one function call
to render more than one primitive such as triangle strip, triangle fan,
etc.
Additionally, this extension adds a further built-in variable, gl_DrawID
to the shading language. This variable contains the index of the draw
currently being processed by a Multi* variant of a drawing command.
IP Status
No known IP claims.
New Procedures and Functions
void MultiDrawArraysANGLE(enum mode,
const int *firsts,
const sizei *counts,
sizei drawcount);
void MultiDrawElementsANGLE(enum mode,
const sizei *counts,
enum type,
const void *const *indices,
sizei drawcount);
void MultiDrawArraysInstancedANGLE(enum mode,
const int *firsts,
const sizei *counts,
const sizei *instanceCounts,
sizei drawcount);
void MultiDrawElementsInstancedANGLE(enum mode,
const sizei *counts,
enum type,
const void *const *indices,
const sizei *instanceCounts,
sizei drawcount);
New Tokens
None.
Additions to Chapter 2 of the OpenGL ES 2.0 Specification
Section 2.8 Vertex Arrays:
The command
void MultiDrawArraysANGLE(
enum mode,
const int *firsts,
const sizei *counts,
sizei drawcount)
Behaves identically to DrawArrays except that a list of arrays is
specified instead. The number of lists is specified in the drawcount
parameter. It has the same effect as:
for(i=0; i<drawcount; i++) {
if (*(counts+i)>0) DrawArrays(mode, *(firsts+i), *(counts+i));
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID>.
The command
void MultiDrawElementsANGLE(
enum mode,
const sizei *counts,
enum type,
const void *const *indices,
sizei drawcount)
Behaves identically to DrawElements except that a list of arrays is
specified instead. The number of lists is specified in the drawcount
parameter. It has the same effect as:
for(i=0; i<drawcount; i++) {
if (*(counts+i)>0) {
DrawElements(mode, *(counts+i), type, *(indices+i));
}
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID>.
Additions to Chapter 2 of the OpenGL ES 3.0 Specification
Section 2.9.3 Drawing Commands:
The command
void MultiDrawArraysInstancedANGLE(
enum mode,
const int *firsts,
const sizei *counts,
const sizei *instanceCounts,
sizei drawcount)
Behaves identically to DrawArraysInstanced except that a list of arrays is
specified instead. The number of lists is specified in the drawcount
parameter. It has the same effect as:
for(i=0; i<drawcount; i++) {
if (*(counts+i)>0) DrawArraysInstanced(mode, *(firsts+i), *(counts+i),
*(instanceCounts+1));
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID>.
The command
void MultiDrawElementsInstancedANGLE(
enum mode,
sizei *counts,
enum type,
const void *const *indices,
const sizei *instanceCounts,
sizei drawcount)
Behaves identically to DrawElementsInstanced except that a list of arrays is
specified instead. The number of lists is specified in the drawcount
parameter. It has the same effect as:
for(i=0; i<drawcount; i++) {
if (*(counts+i)>0) {
DrawElementsInstanced(mode, *(counts+i), type,
*(indices+i), *(instanceCounts+1));
}
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID>.
Errors
The error INVALID_VALUE is generated by the new functions if <drawcount>
is less than 0.
MultiDrawArraysANGLE, MultiDrawElementsANGLE,
MultiDrawArraysInstancedANGLE, and MultiDrawElementsInstancedANGLE generate
the same errors as DrawArrays, DrawElements, DrawArraysInstanced,
and DrawElementsInstanced, respectively, for any draw <i> where an error
is generated. If any call would produce an error, no drawing is performed.
Modifications to the OpenGL ES Shading Language Specification, Version 3.00
Including the following line in a shader can be used to control the
language featured described in this extension:
#extension GL_ANGLE_multi_draw : <behavior>
where <behavior> is as specified in section 3.5.
A new preprocessor #define is added to the OpenGL ES Shading Language:
#define GL_ANGLE_multi_draw 1
Dependencies on GL_ANGLE_instanced_arrays
If GL_ANGLE_instanced_arrays or GL_EXT_instanced_arrays is enabled,
append the lanuage in "Additions to Chapter 2 of the OpenGL ES 3.0
Specification, Section 2.9.3 Drawing Commands" to the language in
"Additions to Chapter 2 of the OpenGL ES 2.0 Specification, Section
2.8 Vertex Arrays".
If GL_ANGLE_instanced_arrays or GL_EXT_instanced_arrays is not enabled
and the context is less than a OpenGL ES 3.0 context, the error
INVALID_OPERATION is generated by any call to the functions
MultiDrawArraysInstancedANGLE and MultiDrawElementsInstancedANGLE.
Issues
None
Revision History
Rev. Date Author Changes
---- -------- ---------------- --------------------------------------------
1 10/24/18 Austin Eng First revision.
2 10/25/18 Austin Eng Add instanced variants.
3 06/21/22 Alexey Knyazev Fixed typos and type usage.
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