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Name
ANGLE_base_vertex_base_instance
Name Strings
GL_ANGLE_base_vertex_base_instance
Contributors
Shrek Shao, Google Inc.
Contributors to the OES_draw_elements_base_vertex specification
Contributors to the EXT_draw_elements_base_vertex specification
Contributors to the EXT_multi_draw_arrays specification
Contributors to the ARB_shader_draw_parameters specification
Contact
Shrek Shao (shrekshao 'at' google.com)
Status
Incomplete
Version
Last Modified Date: Nov 19, 2021
Author Revision: 3
Number
OpenGL ES Extension XX
Dependencies
OpenGL ES 3.1 is required.
This extension is written against the OpenGL ES 3.1 specification, the
OpenGL ES 3.2 specification, and the OpenGL ES Shading Language 3.0
specification.
GL_ANGLE_multi_draw is required.
Overview
This extension exposes the *BaseVertex* draw call in
OES_draw_elements_base_vertex/EXT_draw_elements_base_vertex together with
their newly added *BaseInstance and MultiDraw* variants in addition to the
vertex shader builtins <gl_BaseVertex> and <gl_BaseInstance> exposed by
ARB_shader_draw_parameters for OpenGL.
*BaseInstance behaves identically to its counterpart draw calls except that
<instanceCount> instances of the range of elements are executed and the
value of <instance> advances for each iteration. Those attributes that have
non-zero values for <divisor>, as specified by VertexAttribDivisor, advance
once per <divisor> instances of the set(s) of vertices being rendered.
Additionally, <baseInstance> specifies the first element within the
instanced vertex attributes.
*BaseVertex* is equivalent to its counterpart draw calls except that
the value of the base vertex passed into the driver is <baseVertex> instead
of zero, and that <instances> of the set of elements are executed and the
value of <instance> advances between each set.
IP Status
No known IP claims.
New Procedures and Functions
void DrawArraysInstancedBaseInstanceANGLE(enum mode,
int first,
sizei count,
sizei instanceCount,
uint baseInstance);
void DrawElementsInstancedBaseVertexBaseInstanceANGLE(enum mode,
sizei count,
enum type,
const void *indices,
sizei instanceCount,
int baseVertex,
uint baseInstance);
void MultiDrawArraysInstancedBaseInstanceANGLE(enum mode,
const int *firsts,
const sizei *counts,
const sizei *instanceCounts,
const uint *baseInstances,
sizei drawcount);
void MultiDrawElementsInstancedBaseVertexBaseInstanceANGLE(enum mode,
const sizei *counts,
enum type,
const void *const *indices,
const sizei *instanceCounts,
const int *baseVertices,
const uint *baseInstances,
sizei drawcount);
New Tokens
None.
Additions to Chapter 10 of the OpenGL ES 3.2 Specification
Section 10.5 Drawing Commands Using Vertex Arrays:
The command
void DrawArraysInstancedBaseInstanceANGLE(
enum mode,
int first,
sizei count,
sizei instanceCount,
uint baseInstance);
Behaves identically to DrawArraysInstanced except that <baseInstance> is
passed down to DrawArraysOneInstance instead of zero.
The command
void MultiDrawArraysInstancedBaseInstanceANGLE(
enum mode,
const int *firsts,
const sizei *counts,
const sizei *instanceCounts,
const uint *baseInstances,
sizei drawcount);
Behaves identically to DrawArraysInstancedBaseInstanceANGLE 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) DrawArraysInstancedBaseInstance(
mode,
*(counts+i),
*(instanceCounts+i),
*(firsts+i),
*(baseInstance+i)
);
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID> which is defined in GL_ANGLE_multi_draw.
The command
void DrawElementsInstancedBaseVertexBaseInstanceANGLE(
enum mode,
sizei count,
enum type,
const void *indices,
sizei instanceCount,
int baseVertex,
uint baseInstance);
Behaves identically to DrawElementsInstanced except that <baseVertex> and
<baseInstance> are passed down to DrawElementsOneInstance instead of zero.
The command
void MultiDrawElementsInstancedBaseVertexBaseInstanceANGLE(
enum mode,
const sizei *counts,
enum type,
const void *const *indices,
const sizei *instanceCounts,
const int *baseVertices,
const uint *baseInstances,
sizei drawcount);
Behaves identically to DrawElementsInstancedBaseVertexBaseInstanceANGLE
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) DrawElementsInstancedBaseVertexBaseInstanceANGLE(
mode,
*(counts+i),
type,
*(instanceCounts+i),
*(indices+i),
*(baseVertices+i),
*(baseInstances+i)
);
}
The index of the draw (<i> in the above pseudo-code) may be read by
a vertex shader as <gl_DrawID> which is defined in GL_ANGLE_multi_draw.
Errors
DrawArraysInstancedBaseInstanceANGLE and
DrawElementsInstancedBaseVertexBaseInstanceANGLE
generate the same errors as DrawArraysInstanced and DrawElementsInstanced.
MultiDrawArraysInstancedBaseInstanceANGLE and
MultiDrawElementsInstancedBaseVertexBaseInstanceANGLE
generate the same errors as DrawArraysInstanced and DrawElementsInstanced,
respectively, for any draw <i> where an error is generated. If any call
would produce an error, no drawing is performed.
The error INVALID_VALUE is generated by the MultiDraw* functions if
<drawcount> is less than zero.
Dependencies on GL_OES_draw_elements_base_vertex and
GL_EXT_draw_elements_base_vertex
If the OpenGL ES context version is less than 3.2, this extension is only
available when GL_OES_draw_elements_base_vertex or
GL_EXT_draw_elements_base_vertex are available.
Issues
None
Revision History
Rev. Date Author Changes
---- -------- ---------------- --------------------------------------------
1 08/13/19 Shrek Shao First revision.
2 07/14/20 Shrek Shao Fix baseInstance type from GLint to GLuint.
3 11/19/21 Shrek Shao Decouple gl_BaseVertex/gl_BaseInstance.
4 06/21/22 Alexey Knyazev Fixed typos and type usage.
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