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Name Strings
Piers Daniell, NVIDIA Corporation (pdaniell 'at'
Daniel Koch, NVIDIA Corporation (dkoch 'at'
and contributors to the OpenGL ES 3.2 specification
Copyright (c) 2015 The Khronos Group Inc. Copyright terms at
Specification Update Policy
Khronos-approved extension specifications are updated in response to
issues and bugs prioritized by the Khronos OpenGL Working Group. For
extensions which have been promoted to a core Specification, fixes will
first appear in the latest version of that core Specification, and will
eventually be backported to the extension document. This policy is
described in more detail at
Complete. Approved by the ARB on June 26, 2015.
Ratified by the Khronos Board of Promoters on August 7, 2015.
Last Modified Date: June 25, 2015
Revision: 8
ARB Extension #177
OpenGL 4.5, ARB_ES2_compatibility, ARB_ES3_compatibility and
ARB_ES3_1_compatibility are required.
KHR_blend_equation_advanced and KHR_texture_compression_astc_ldr are
recommended to support the full OpenGL ES 3.2 feature set, but not
required for this extension.
This extension is written against The OpenGL 4.5 (Compatibility Profile)
This extension adds support for features of OpenGL ES 3.2 that are
missing from OpenGL 4.5. Enabling these features will ease the process
of porting applications from OpenGL ES 3.2 to OpenGL.
In particular this adds the following features:
- Bounding box used to optimization tessellation processing
- support for the OpenGL ES 3.20 shading language
For full OpenGL ES 3.2 compatibility the implementation must support
KHR_blend_equation_advanced and KHR_texture_compression_astc_ldr. Those
features are not defined in this extension spec since they are already
defined at the KHR level.
New Procedures and Functions
void PrimitiveBoundingBoxARB(float minX, float minY, float minZ, float minW,
float maxX, float maxY, float maxZ, float maxW);
New Tokens
Accepted by the <pname> parameter of GetBooleanv, GetFloatv, GetIntegerv,
and GetInteger64v:
Additions to Chapter 11 of the 4.5 Specification (Programmable Vertex
-- OpenGL: Section 11.2, Tessellation
Modify section, "Tessellation Control Shader Outputs":
In the second paragraph, add gl_BoundingBox[] to the list of built-in
per-patch output arrays:
Tessellation shaders additionally have three built-in per-patch output
arrays, gl_TessLevelOuter[], gl_TessLevelInner[], and gl_BoundingBox[].
These arrays ... as discussed in the following section. gl_BoundingBox[]
is an array of two vec4 values that should be used instead of the value of
PRIMITIVE_BOUNDING_BOX_ARB as the primitive bounding box (see Section
14.1pbb) for primitives generated from the output patch.
Modify the sixth paragraph of the section to state that gl_BoundingBox[]
counts against the per-patch limit:
... The built-in outputs gl_TessLevelOuter[] and gl_TessLevelInner[] are not
counted against the per-patch limit. The built-in output
gl_BoundingBox[], if statically assigned by the shader, is counted
against the per-patch limit. The total number of components...
Modify section, "Tessellation Evaluation Shader Inputs":
Insert a new paragraph after the list of special input variables in
paragraph 2:
The special tessellation control shader output gl_BoundingBox[] is
consumed by the tessellation primitive generator, and is not available as an
input to the tessellation evaluation shader.
Add new section 14.1pbb following section 14.1, "Discarding Primitives
Before Rasterization" on p. 525:
14.1pbb, Primitive Bounding Box
Implementations may be able to optimize performance if the application
provides bounds of primitives that will be generated by the tessellation
primitive generator or the geometry shader prior to executing those stages.
If the provided bounds are incorrect and primitives extend beyond them, the
rasterizer may or may not generate fragments for the portions of primitives
outside the bounds.
The primitive bounding box is specified using
void PrimitiveBoundingBoxARB(float minX, float minY, float minZ, float minW,
float maxX, float maxY, float maxZ, float maxW);
where <minX>, <minY>, <minZ>, and <minW> specify the minimum clip space
coordinate of the bounding box and <maxX>, <maxY>, <maxZ>, and <maxW>
specify the maximum coordinate.
If tessellation is active, each invocation of the tessellation control
shader may re-specify the bounding box by writing to the built-in
gl_BoundingBox[] variable. If the shader statically assigns a value to
any part of this variable, then gl_BoundingBox[0] is used instead of
<minX>, <minY>, <minZ>, <minW>, and gl_BoundingBox[1] is used instead of
<maxX>, <maxY>, <maxZ>, <maxW>. If the shader contains a static assignment
to gl_BoundingBox[] and there is an execution path through the shader
that does not write all components of gl_BoundingBox[], the value of
unwritten components and corresponding bounding box coordinates is undefined
for executions of the shader that take that path.
If the tessellation control shader re-specifies the bounding box, the re-
specified value is used for primitives generated from the output patch by
the primitive generator, any primitives emitted by the geometry shader
invocations for those generated primitives, and any primitives further
introduced during clipping.
The bounding box in clip space is composed of 16 vertices formed by all
combinations of the minimum and maximum values for each dimension. This
bounding box is clipped against w_c > 0, and projected to three dimensions
by dividing x_c, y_c, and z_c by w_c for each vertex. The viewport transform
is then applied to each vertex to produce a three-dimensional bounding
volume in window coordinates.
The window space bounding volume is expanded in the X and Y dimensions to
accomodate the rasterization rules for the primitive type, and to fall on
fragment boundaries:
min_wc' = floor(min_wc - size/2.0)
max_wc' = ceil(max_wc + size/2.0)
where the min_wc rule is used for x and y window coordinates of bounding
volume vertices formed from minX and minY respectively, and the max_wc rule
is used for x and y window coordinates of bounding volume vertices formed
from maxX and maxY respectively. For point primitives, size is the per-
primitive point size after clamping to the implementation-defined maximum
point size as described in section 13.3. For line primitives, size is the
line width, after rounding and clamping as described in section
For triangle primitives, size is zero.
During rasterization, the rasterizer will generate fragments with
window coordinates inside the windows space bounding volume, but may or may
not generate fragments with window coordinates outside the bounding volume.
Modify section 14.5.4, "Line Multisample Rasterization":
Replace the last paragraph with:
Line width range and number of gradations are equivalent to those supported
for antialiased lines. The supported [min, max] range of multisampled line
widths, and the width of evenly-space graduations within that range are
implementation-dependent and may be queried as
respectively, as described in table 23.54. If, for instance the width range
is from 0.1 to 2.0 and the gradation width is 0.1 then the widths 0.1, 0.2,
..., 1.9, 2.0 are supported. Additional line widths may also be supported;
there is no requirement that these widths be evenly space. If an
unsupported width is requested, the nearest supported width is used
Additions to the OpenGL Shading Language
Including the following line in a shader can be used to control the
language features described in this extension:
#extension GL_ARB_ES3_2_compatibility : <behavior>
where <behavior> is as specified in section 3.3.
New preprocessor #defines are added to the OpenGL Shading Language:
#define GL_ARB_ES3_2_compatibility 1
Additions to Chapter 3 of the OpenGL Shading Language 4.50.5 Specification
Modify the paragraph at the bottom of page 16 in Section 3.3
(Preprocessor) as follows:
"... Shaders that specify #version 100 will be treated as targeting
version 1.00 of the OpenGL ES Shading Language. Shaders that specify
#version 300 will be treated as targeting version 3.00 of the OpenGL
ES Shading Language. Shaders that specify #version 310 will be treated
as targeting version 3.10 of the OpenGL ES Shading Language. Shaders
that specify #version 320 will be treated as targeting version 3.20
of the OpenGL ES Shading Language...."
Modify the 3rd paragraph at the top of p16 as follows:
A <profile> argument ...
If version 300, 310 or 320 is specified, the profile argument is not
optional and must be "es", or a compile-time error results. The Language
Specification ...
Additions to Chapter 7 of the OpenGL Shading Language 4.50.5 Specification
(Built-in Variables)
Add a new built-in variable intrinsic declaration after the
gl_TessLevelOuter and gl_TessLevelInner declarations:
patch out highp vec4 gl_BoundingBox[2];
Additions to the AGL/GLX/WGL Specifications
New State
Add to state values in Table 23.10, Transformation State:
Get Value Type Get Command Value Description Sec.
-------------------------- ---- ----------- ------------ ----------------- --------
PRIMITIVE_BOUNDING_BOX_ARB 8xR GetFloatv -1,-1,-1, 1, Default primitive 14.1pbb
1, 1, 1, 1 bounding box
Add to state values in Table 23.54, Implementation Dependent Values:
Get Value Type Get Command Value Description Sec.
-------------------------------- ---- ----------- ------- ------------------- --------
MULTISAMPLE_LINE_WIDTH_RANGE_ARB 2xR+ GetFloatv 1,1 Range (lo to hi) of 14.5.4
multisampled line widths
MULTISAMPLE_LINE_WIDTH_GRANULARITY_ARB R+ GetFloatv - Multisampled line 14.5.4
width granularity
1) With this extension, is OpenGL 4.5 a complete superset of OpenGL ES 3.2?
RESOLVED: No. This extension does not include KHR_blend_equation_advanced or
KHR_texture_compression_astc_ldr even though these are part of OpenGL ES 3.2.
These continue to be optional extensions for OpenGL. Otherwise OpenGL 4.5
plus this extension is a superset of OpenGL ES 3.2.
Revision History
Rev. Date Author Changes
---- -------- -------- -----------------------------------------------
1 04/19/15 pdaniell Initial draft with incomplete text.
2 04/29/15 pdaniell Remove EXT_texture_sRGB_decode which is no longer
in OpenGL ES 3.2.
3 05/07/15 dkoch Add MULTISAMPLED_LINE_WIDTH_RANGE_ARB query
(Bug 13828).
Remove ASTC interaction with SRGB_DECODE.
4 05/07/15 Jon Leech Assign enum for MULTISAMPLED_LINE_WIDTH_RANGE_ARB.
5 05/21/15 pdaniell Allow KHR_blend_equation_advanced and
KHR_texture_compression_astc_ldr to be optional
for this extension.
6 06/18/15 pdaniell Fix resolution of issue (1).
spelling (drop 'D')
query per bug 13828.