Name
OES_EGL_image_external
Name Strings
GL_OES_EGL_image_external
Contributors
Acorn Pooley
David Garcia
Bruce Merry
Aske Simon Christensen
Mark Callow
Tom Olson
Jon Leech
Maurice Ribble
Contacts
Acorn Pooley, NVIDIA Corporation (apooley 'at' nvidia.com)
Notice
Copyright (c) 2009-2013 The Khronos Group Inc. Copyright terms at
http://www.khronos.org/registry/speccopyright.html
Specification Update Policy
Khronos-approved extension specifications are updated in response to
issues and bugs prioritized by the Khronos OpenGL ES 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
https://www.khronos.org/registry/OpenGL/docs/update_policy.php
Status
Ratified by Khronos Promoters, 10 December 2010
Approved by the OpenGL ES Working Group, 15 September 2010
Version
April 6, 2018 (version 25)
Number
OpenGL ES Extension #87
Dependencies
Requires OpenGL ES 1.1 or OpenGL ES 2.0.
Requires EGL 1.2
Requires either the EGL_KHR_image_base or the EGL_KHR_image extension
This extension is written based on the wording of the OpenGL ES 2.0
specification, the OpenGL ES Shading Language version 1.0, and the
EGL_KHR_image_base extension. On an OpenGL ES 2.0 implementation, ignore
sections which are added only to the OpenGL ES 1.1 specification.
This extension is also written based on the wording of the OpenGL ES 1.1
specification. On an OpenGL ES 1.X implementation, ignore sections which
are added only to the OpenGL ES 2.0 or OpenGL ES Shading Language
specification. Also ignore all mention of MAX_VERTEX_TEXTURE_IMAGE_UNITS,
and MAX_COMBINED_TEXTURE_IMAGE_UNITS.
This extension borrows concepts and function names from the
GL_OES_EGL_image extension. This extension is compatible with, but does
not require, the GL_OES_EGL_image extension.
Overview
This extension provides a mechanism for creating EGLImage texture targets
from EGLImages. This extension defines a new texture target,
TEXTURE_EXTERNAL_OES. This texture target can only be specified using an
EGLImage. There is no support for most of the functions that manipulate
other texture targets (e.g. you cannot use gl*Tex*Image*() functions with
TEXTURE_EXTERNAL_OES). Also, TEXTURE_EXTERNAL_OES targets never have more
than a single LOD level. Because of these restrictions, it is possible to
bind EGLImages which have internal formats not otherwise supported by
OpenGL ES. For example some implementations may allow EGLImages with
planar or interleaved YUV data to be GLES texture target siblings. It is
up to the implementation exactly what formats are accepted.
Glossary
Please see the EGL_OES_image_base specification for a list of terms
used by this specification.
New Types
/*
* GLeglImageOES is an opaque handle to an EGLImage
* Note: GLeglImageOES is also defined in GL_OES_EGL_image
*/
typedef void* GLeglImageOES;
/* (OpenGL ES 2.x only)
* New sampler type allowed by the OpenGL ES Shading Language when
* #extension GL_OES_EGL_image_external
* is used.
*/
samplerExternalOES
New Procedures and Functions
/* Note: EGLImageTargetTexture2DOES is also defined in GL_OES_EGL_image */
void EGLImageTargetTexture2DOES(enum target, eglImageOES image)
New Tokens
Accepted as a target in the <target> parameter of BindTexture and
EGLImageTargetTexture2DOES:
TEXTURE_EXTERNAL_OES 0x8D65
(OpenGL ES 2.x only) Returned in the <type> parameter of GetActiveUniform:
SAMPLER_EXTERNAL_OES 0x8D66
Accepted as the <pname> parameter of GetBooleanv, GetIntegerv,
GetFloatv, and GetFixedv:
TEXTURE_BINDING_EXTERNAL_OES 0x8D67
Accepted as <value> in GetTexParameter*() queries:
REQUIRED_TEXTURE_IMAGE_UNITS_OES 0x8D68
Additions to Chapter 3 of the OpenGL 1.1 or OpenGL 2.0 Specification
- For OpenGL ES 2.0 add a new section: "3.7.14 External Textures," which
follows section "3.7.13 Texture Objects." For OpenGL ES 1.1 add a new
section after section "3.7.11 Texture Objects."
"3.7.14 External Textures
External textures cannot be used with TexImage2D, TexSubImage2D,
CompressedTexImage2D, CompressedTexSubImage2D, CopyTexImage2D, or
CopyTexSubImage2D, and an INVALID_ENUM error will be generated if this
is attempted. Their default min filter is LINEAR. It is an
INVALID_ENUM error to set the min filter value to anything other than
LINEAR or NEAREST. The default s and t wrap modes are CLAMP_TO_EDGE
and it is an INVALID_ENUM error to set the wrap mode to any other
value. (For OpenGL ES 1.x only: The texture parameter GENERATE_MIPMAP
is always FALSE, and setting it to any other value generates an
INVALID_ENUM error. (For OpenGL ES 2.x only: Calling GenerateMipmaps
with <target> set to TEXTURE_EXTERNAL_OES results in an INVALID_ENUM.)
The command
void EGLImageTargetTexture2DOES(enum target, eglImageOES image);
with <target> set to TEXTURE_EXTERNAL_OES defines the currently bound
external texture object to be a target sibling of <image>. The width,
height, format, type, internalformat, border, and image data are all
determined based on the specified eglImageOES <image>. Any sibling
previously associated with this external texture object is deleted.
A EGLImageTargetTexture2DOES() call with <target> set to
TEXTURE_EXTERNAL_OES will not modify the pixel data values in the
EGLImage.
<image> must be the handle of a valid EGLImage resource, cast into the
type eglImageOES.
Assuming no errors are generated in EGLImageTargetTexture2DOES, the
newly specified texture object will be an EGLImage target of the
specified eglImageOES.
If the GL is unable to specify a texture object using the supplied
eglImageOES <image> (if, for example, <image> refers to a multisampled
eglImageOES), the error INVALID_OPERATION is generated.
If <target> is not TEXTURE_EXTERNAL_OES, the error INVALID_ENUM is
generated. (Note: if GL_OES_EGL_image is supported then <target> may
also be TEXTURE_2D).
Sampling an external texture which is not associated with any EGLImage
sibling will return a sample value of (0,0,0,1).
Each TEXTURE_EXTERNAL_OES texture object may require up to 3 texture
image units for each texture unit to which it is bound. The number of
texture image units required by a bound texture object can be queried
using GetTexParameteriv() with <target> set to the texture target in
question, <value> set to REQUIRED_TEXTURE_IMAGE_UNITS_OES, and
ActiveTexture set to the texture unit to which the texture object is
bound. When <target> is set to TEXTURE_EXTERNAL_OES this value will
be between 1 and 3 (inclusive). For other valid texture targets this
value will always be 1. Note that, when a TEXTURE_EXTERNAL_OES
texture object is bound, the number of texture image units required by
a single texture unit may be 1, 2, or 3, while for other texture
objects each texture unit requires exactly 1 texture image unit.
(For OpenGL ES 1.x only) DrawArrays and DrawElements will fail and
generate an INVALID_OPERATION error if the number of texture image
units required is greater than the number available. The number of
required texture image units is equal to the sum of the requirements
for each enabled texture unit. For each texture unit the requirement
is the value returned by GetTexParameteriv() when <value> is set to
REQUIRED_TEXTURE_IMAGE_UNITS_OES, <target> is set to the target which
is enabled, and ActiveTexture has been set to the texture unit in
question.
(For OpenGL ES 2.x only) DrawArrays and DrawElements will fail and
generate an INVALID_OPERATION error if the number of texture image
units required is greater than the number available. The number of
required texture image units for each stage (fragment or vertex) is
equal to the sum of the requirements for each sampler referenced by
the stage. A sampler is considered referenced if its location
(returned by GetUniformLocation) is not -1. For each referenced
sampler the requirement is the value returned by GetTexParameteriv()
when <value> is set to REQUIRED_TEXTURE_IMAGE_UNITS_OES, <target> is
set to the target corresponding to the sampler type, and ActiveTexture
has been set to the texture unit corresponding to the value of the
sampler uniform. The condition can be detected by calling Validate.
(For OpenGL ES 2.x only) A shader that uses external texture samplers
may require some number of hidden uniform variables to implement the
conversion from YUV to RGB, and this may reduce the amount of space
available for uniforms defined by the shader program. This may cause
a shader program which was working to stop working when a different
external texture is used (i.e. when Uniform1i or BindTexture is
called). If there are not enough uniforms available then calls to
DrawArrays or DrawElements will fail and generate an INVALID_OPERATION
error. This condition can be detected by calling ValidateProgram.
Sampling an external texture which has been modified since it was
bound will return samples which may correspond to image values either
before, during, or after the modification. Binding (or re-binding if
already bound) an external texture by calling BindTexture after all
modifications are complete guarantees that sampling done in future
draw calls will return values corresponding to the values in the
buffer at or after the time that BindTexture is called. (Note that
calling BindTexture after calling commands that modify the EGLImage
may not be sufficient to ensure that the modifications are complete;
additional synchronization (for example eglWaitAPI, eglWaitNative,
glFinish, vgFinish, or eglWaitSyncKHR, etc) may be required following
the call initiating modifications, to ensure they have taken effect on
the texture, before the call to BindTexture is made.)
Sampling an external texture will return an RGBA vector in the same
colorspace as the source image. If the source image is stored in YUV
(or some other basis) then the YUV values will be transformed to RGB
values. (But these RGB values will be in the same colorspace as the
original image. Colorspace here includes the linear or non-linear
encoding of the samples. For example, if the original image is in the
sRGB color space then the RGB value returned by the sampler will also
be sRGB, and if the original image is stored in ITU-R Rec. 601 YV12
then the RGB value returned by the sampler will be an RGB value in the
ITU-R Rec. 601 colorspace.) The parameters of the transformation
from one basis (e.g. YUV) to RGB (color conversion matrix, sampling
offsets, etc) are taken from the EGLImage which is associated with the
external texture. The implementation may choose to do this
transformation when the external texture is sampled, when the external
texture is bound, or any other time so long as the effect is the same.
It is undefined whether texture filtering occurs before or after the
transformation to RGB.
If the EGLImage associated with the external texture contains alpha
values then the value of the alpha component returned is taken from
the image; otherwise the alpha component is 1.0.
Changes to section "2.10.4 Shader Variables" of the OpenGL ES 2.0
specification (ignore for OpenGL ES 1.x)
- In the subsection "Uniform Variables" paragraph 13, last sentence, add
"SAMPLER_EXTERNAL_OES"
to the list of types that can be returned.
Changes to section "2.10.5 Shader Execution" of the OpenGL ES 2.0
specification (ignore for OpenGL ES 1.x)
- In the subsection "Validation", add to the bullet points in the second
paragraph:
"- the number of texture image units required is greater than
the number available (see REQUIRED_TEXTURE_IMAGE_UNITS_OES,
MAX_COMBINED_TEXTURE_IMAGE_UNITS, MAX_VERTEX_TEXTURE_IMAGE_UNITS,
and MAX_TEXTURE_IMAGE_UNITS).
- the number of uniforms required to implement the shader program is
greater than the number available."
Changes to section "3.7.5 Texture Parameters" of the OpenGL ES 1.1 specification
- Add to the end of the section a new paragraph:
"When <target> is TEXTURE_EXTERNAL_OES only NEAREST and LINEAR are
accepted as TEXTURE_MIN_FILTER, only CLAMP_TO_EDGE is accepted as
TEXTURE_WRAP_S and TEXTURE_WRAP_T, and only FALSE is accepted as
GENERATE_MIPMAP. Attempting to set other values for
TEXTURE_MIN_FILTER, TEXTURE_WRAP_S, TEXTURE_WRAP_T, or GENERATE_MIPMAP
will result in an INVALID_ENUM error.
Changes to section "3.7.4 Texture Parameters" of the OpenGL ES 2.0 Specification
- Add to the end of the section a new paragraph:
"When <target> is TEXTURE_EXTERNAL_OES only NEAREST and LINEAR are
accepted as TEXTURE_MIN_FILTER and only CLAMP_TO_EDGE is accepted as
TEXTURE_WRAP_S and TEXTURE_WRAP_T. Attempting to set other values for
TEXTURE_MIN_FILTER, TEXTURE_WRAP_S, or TEXTURE_WRAP_T will result in
an INVALID_ENUM error.
Changes to section "3.7.10 Texture State" of the OpenGL ES 1.1 Specification
and section "3.7.12 Texture State" of the OpenGL ES 2.0 Specification
- Add an additional sentence at the end of the section:
"In the initial state of a TEXTURE_EXTERNAL_OES texture object,
the value assigned to TEXTURE_MIN_FILTER and TEXTURE_MAG_FILTER is
LINEAR, and the s and t wrap modes are both set to
CLAMP_TO_EDGE."
Changes to section "3.7.11 Mipmap Generation" of the OpenGL ES 2.0 Specification
(ignore for OpenGL ES 1.x)
- Add two additional paragraphs to the end of the section:
"When <target> is set to TEXTURE_EXTERNAL_OES, GenerateMipmap
always fails and generates an INVALID_ENUM error."
Changes to section "3.7.11 Texture Objects" of the OpenGL ES 1.1 specification
(ignore for OpenGL ES 2.x)
- Modify this section as follows: (changed lines marked with *, and added
lines are marked with +)
* "In addition to the default textures TEXTURE_2D and
* TEXTURE_EXTERNAL_OES, named two-dimensional and external texture
objects can be created and operated upon. The name space for texture
objects is the unsigned integers, with zero reserved by the GL.
A texture object is created by binding an unused name to
* TEXTURE_2D or TEXTURE_EXTERNAL_OES. The binding is effected by calling
void BindTexture( enum target, uint texture );
* with target set to the desired texture target and texture set to the
unused name. The resulting texture object is a new state vector,
comprising all the state values listed in section 3.7.10, set to the
+ same initial values. If the new texture object is bound to TEXTURE_2D
+ or TEXTURE_EXTERNAL_OES it is and remains a two-dimensional or
+ external texture respectively until it is deleted.
BindTexture may also be used to bind an existing texture object to
* TEXTURE_2D or TEXTURE_EXTERNAL_OES. If the bind is successful no
change is made to the state of the bound texture object, and any
previous binding to target is broken.
While a texture object is bound, GL operations on the target to
which it is bound affect the bound object, and queries of the target
to which it is bound return state from the bound object. If texture
mapping is enabled, the state of the bound texture object directs the
texturing operation.
* In the initial state, TEXTURE_2D and TEXTURE_EXTERNAL_OES have
* two-dimensional and external texture state vectors respectively
* associated with them. In order that access to these initial textures
* not be lost, they are treated as texture objects all of whose names
* are 0. The initial two-dimensional and external texture are therefore
* operated upon, queried, and applied as TEXTURE_2D or
* TEXTURE_EXTERNAL_OES respectively while 0 is bound to the
* corresponding targets.
Texture objects are deleted by calling
void DeleteTextures( sizei n, uint *textures );
textures contains n names of texture objects to be deleted. After a
texture object is deleted, it has no contents, and its name is again
unused. If a texture that is currently bound to the target TEXTURE_2D
* or TEXTURE_EXTERNAL_OES is deleted, it is as though BindTexture had
been executed with the same target and texture zero. Unused names in
textures are silently ignored, as is the value zero.
The command
void GenTextures( sizei n, uint *textures );
returns n previously unused texture object names in textures. These
names are marked as used, for the purposes of GenTextures only, but
they acquire texture state only when they are first bound, just as if
they were unused.
The texture object name space, including the initial texture
object, is shared among all texture units. A texture object may be
bound to more than one texture unit simultaneously. After a texture
object is bound, any GL operations on that target object affect any
other texture units to which the same texture object is bound.
Texture binding is affected by the setting of the state
ACTIVE_TEXTURE.
If a texture object is deleted, it is as if all texture units which
are bound to that texture object are rebound to texture object zero.
Changes to section "3.7.13 Texture Objects" of the OpenGL ES 2.0 specification
(ignore for OpenGL ES 1.x)
- Modify this section as follows: (changed lines marked with *, and added
lines are marked with +)
* "In addition to the default textures TEXTURE_2D, TEXTURE_CUBE_MAP,
* and TEXTURE_EXTERNAL_OES, named two-dimensional, cube map, and
external texture objects can be created and operated upon. The name
space for texture objects is the unsigned integers, with zero reserved
by the GL.
A texture object is created by binding an unused name to
* TEXTURE_2D, TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL_OES. The binding is
effected by calling
void BindTexture( enum target, uint texture );
with target set to the desired texture target and texture set to the
unused name. The resulting texture object is a new state vector,
comprising all the state values listed in section 3.7.12, set to the
same initial values. If the new texture object is bound to TEXTURE_2D,
* TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL_OES it is and remains a
* two-dimensional, cube map, or external texture respectively until it
is deleted.
BindTexture may also be used to bind an existing texture object to
* either TEXTURE_2D, TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL_OES. The error
INVALID_OPERATION is generated if an attempt is made to bind a texture
* object of different target than the specified target. If the bind is
successful no change is made to the state of the bound texture object,
and any previous binding to target is broken.
While a texture object is bound, GL operations on the target to
which it is bound affect the bound object, and queries of the target to
which it is bound return state from the bound object. If texture
mapping is enabled, the state of the bound texture object directs the
texturing operation.
* In the initial state, TEXTURE_2D, TEXTURE_CUBE_MAP, and
* TEXTURE_EXTERNAL_OES have two-dimensional, cube map, and external
texture state vectors respectively associated with them. In order
that access to these initial textures not be lost, they are treated as
texture objects all of whose names are 0. The initial two-dimensional,
* cube map, and external texture are therefore operated upon, queried,
* and applied as TEXTURE_2D, TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL_OES
respectively while 0 is bound to the corresponding targets.
Texture objects are deleted by calling
void DeleteTextures( sizei n, uint *textures );
textures contains n names of texture objects to be deleted. After a
texture object is deleted, it has no contents or dimensionality, and
its name is again unused. If a texture that is currently bound to one
* of the targets TEXTURE_2D, TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL_OES
is deleted, it is as though BindTexture had been executed with the
same target and texture zero. Unused names in textures are silently
ignored, as is the value zero.
The command
void GenTextures( sizei n, uint *textures );
returns n previously unused texture object names in textures. These
names are marked as used, for the purposes of GenTextures only, but
they acquire texture state only when they are first bound, just as if
they were unused.
The texture object name space, including the initial texture
object, is shared among all texture units. A texture object may be
bound to more than one texture unit simultaneously. After a texture
object is bound, any GL operations on that target object affect any
other texture units to which the same texture object is bound.
Texture binding is affected by the setting of the state
ACTIVE_TEXTURE.
If a texture object is deleted, it is as if all texture units which
are bound to that texture object are rebound to texture object zero.
Changes to section "3.7.13 Texture Application" of the OpenGL ES 1.1
specification (ignore for OpenGL ES 2.x)
- Replace the first sentence of the first paragraph with:
"Texturing is enabled or disabled using the generic Enable and
Disable commands, with the symbolic constant TEXTURE_2D or
TEXTURE_EXTERNAL_OES to enable or disable texturing with the
TEXTURE_2D or TEXTURE_EXTERNAL_OES texture target, respectively. If
TEXTURE_EXTERNAL_OES is enabled it takes precedence over TEXTURE_2D,
TEXTURE_CUBE_MAP_OES, TEXTURE_RECTANGLE_ARB, and
TEXTURE_RECTANGLE_NV."
Changes to section "3.8.2 Shader Execution" of the OpenGL ES 2.0
specification (ignore for OpenGL ES 1.x)
- Add to the end of the last paragraph of the subsection "Texture Access"
"The REQUIRED_TEXTURE_IMAGE_UNITS_OES parameter can change based on the
number of external textures which are currently bound (see section
3.7.14)."
Changes to section "6.1.3 Enumerated Queries" of the OpenGL ES 1.1 specification
- Change:
"...TEXTURE_2D..."
to
"...TEXTURE_2D or TEXTURE_EXTERNAL..."
in the last paragraph.
Changes to section "6.1.3 Enumerated Queries" of the OpenGL ES 2.0 specification
- Change:
"...TEXTURE_2D or TEXTURE_CUBE_MAP..."
to
"...TEXTURE_2D, TEXTURE_CUBE_MAP, or TEXTURE_EXTERNAL..."
in the second paragraph.
Changes to section "6.2 State Tables" of the OpenGL ES 1.1 specification
- Add to "Table 6.13 Textures (state per texture unit and binding point)"
+-------------------+-------+-------------+-------+------------------+
| TEXTURE_BINDING_- | 8*xZ+ | GetIntegerv | 0 | Texture object |
| EXTERNAL_OES | | | | bound to |
| | | | | TEXTURE_- |
| | | | | EXTERNAL_OES |
+-------------------+-------+-------------+-------+------------------+
| TEXTURE_- | 2*xB | IsEnabled | False | True if external |
| EXTERNAL_OES | | | | texturing is |
| | | | | enabled |
+-------------------+-------+-------------+---+----------------------+
- Add to "Table 6.14 Textures (state per texture object)"
+--------------------+-------+-----------------+---+----------------+
| REQUIRED_TEXTURE_- | n*xZ3 | GetTexParameter | 1 | Number of |
| IMAGE_UNITS_OES | | | | texture image |
| | | | | units required |
| | | | | by texture |
+--------------------+-------+-----------------+---+----------------+
Changes to section "6.2 State Tables" of the OpenGL ES 2.0 specification
- Add to "Table 6.7 Textures (state per texture unit and binding point)"
+-------------------+-------+-------------+-------+------------------+
| TEXTURE_BINDING_- | 8*xZ+ | GetIntegerv | 0 | Texture object |
| EXTERNAL_OES | | | | bound to |
| | | | | TEXTURE_- |
| | | | | EXTERNAL_OES |
+-------------------+-------+-------------+-------+------------------+
- Add to "Table 6.8 Textures (state per texture object)"
+--------------------+-------+-----------------+---+----------------+
| REQUIRED_TEXTURE_- | n*xZ3 | GetTexParameter | 1 | Number of |
| IMAGE_UNITS_OES | | | | texture image |
| | | | | units required |
| | | | | by texture |
+--------------------+-------+-----------------+---+----------------+
Changes to section 3.7 of the OpenGL ES Shading Language specification
- Add to the list of keywords:
"samplerExternalOES"
Changes to section 4.1 of the OpenGL ES Shading Language specification
- Add to the list of basic types:
"samplerExternalOES a handle for accessing an external texture"
Changes to section 4.5.3 of the OpenGL ES Shading Language specification
- Add to the list of "vertex language has the following predeclared
globally scoped default precision statements:"
"precision lowp samplerExternalOES;"
- Add to the list of "fragment language has the following predeclared
globally scoped default precision statements:"
"precision lowp samplerExternalOES;"
Changes to section 8.7 of the OpenGL ES Shading Language specification
- Add to the table the following sampler functions:
"vec4 texture2D(
samplerExternalOES sampler,
vec2 coord)
vec4 texture2DProj(
samplerExternalOES sampler,
vec3 coord)
vec4 texture2DProj(
samplerExternalOES sampler,
vec4 coord)"
Changes to section 9 of the OpenGL ES Shading Language specification
- Add to token list:
"SAMPLEREXTERNAL"
- Add following "type_specifier_no_prec:"
"SAMPLEREXTERNAL"
Changes to section "A.7 Counting of Varyings and Uniforms" of the OpenGL ES
Shading Language specification
- Change the first sentence of the last paragraph to
"Part of the storage may be reserved by an implementation for its own
use e.g. for computation of transcendental functions or conversion of
external textures."
Issues
1. What happens when GenerateMipmaps() is called with <target> set to
TEXTURE_EXTERNAL_OES?
Possible options:
A) Fail (INVALID_ENUM)
B) Generate the mipmaps and copy them into the TEXTURE_2D target.
Option B could be useful and should not be difficult to implement.
What happens when the texture is NPOT and GenerateMipmaps() is called?
Ben Bowman and David Garcia have indicated they prefer A. No other
strong opinions yet.
RESOLVED: A (fail)
2. Should the wrap mode of an external texture be allowed to be anything
other than CLAMP_TO_EDGE?
RESOLVED: no
3. What about portability problems introduced by allowing implementation-
dependent failures?
This is the same issue described in Issue 14 of the
EGL_OES_image specification. Like the resolution for that issue,
this specification should include some minimum requirements, but
leave the larger portability problem unresolved at the moment.
RESOLVED: This and other (EGL_KHR_image_uses and EGL_KHR_il_image)
extensions attempt to minimize this problem by allowing EGL to pick
EGLImage attributes which will work in various situations. However it
is not possible to guarantee that every usecase will work on every
platform.
4. Should EGLImageTargetTexture2DOES result in undefined pixel data,
as with calls to eglCreateImageOES?
See also issue 4 of GL_OES_EGL_image
Comment from Aske:
In the description for EGLImageTargetTexture2DOES, it says: "As a
result of this operation all pixel data in <image> will become
undefined." Why is this? I would imagine one would want to take an
existing EGL image containing image data and bind it as an external
texture, possibly multiple times, to use it for rendering. I have read
through issue 4 of OES_EGL_image, and it seems the concern here is
what happens when the image is (potentially) modified from OpenGL ES.
Since external images cannot be modified from OpenGL ES, I would guess
the same issues do not apply here.
Comment from Acorn:
Another potential issue is that the memory for the EGLImage may
have to be reallocated in order to be compatible with GLES (e.g. GLES
may have more strict alignment or other requirements). However, the
implementation can fail (or do a copy) if this is the case. If the
EGL_KHR_image_uses extension is used to specify that the EGLImage will
be used as a GLES external texture then this should not be an issue
because EGL will be able to allocate the memory correctly in the first
place.
RESOLVED: pixel data will not become undefined when
EGLImageTargetTexture2DOES() is used with an external texture target.
5. What happens if the texture is bound while the associated EGLImage is
being modified.
Some implementations may need to color convert the data
after it has been generated. A solution to this is to state that the
texels become undefined if the external texture is bound while the
underlying texels are modified. This way any color conversion can be
done (e.g. to a second buffer) when the texture is bound.
Options:
A) require the texture be unbound while the EGLImage is being modified
B) Require the texture to be bound (or re-bound if already bound)
between modification and use (i.e. after modification and before
used as a texture).
C) No requirement.
RESOLVED: B
6. How can current generation hardware support planar YUV EGLImage formats?
GLES 2.0 hardware can perform color conversion by inserting
extra instructions into the shader program. However, planar textures
require 2 or 3 surfaces to be read in order to sample a single texture.
One solution is to increase the number of texture image units required
by a texture object which is associated with such an EGLImage.
RESOLVED: allow the implementation to set the number of texture
image units required by each texture object. Allow the app to query
this with REQUIRED_TEXTURE_IMAGE_UNITS_OES. Have drawing commands
fail (INVALID_OPERATION) when the number of texture image units
required by all enabled/referenced texture units exceeds the
implementation limit (which can be queried with
MAX_COMBINED_TEXTURE_IMAGE_UNITS, MAX_VERTEX_TEXTURE_IMAGE_UNITS, and
MAX_TEXTURE_IMAGE_UNITS)
See also issue 10.
7. Should there be new texture sampling functions for samplerExternalOES
or is it OK to use the existing 2D sampler functions.
RESOLVED: Use existing 2D sampler functions.
8. If an EGLImage associated with an external texture does not contain an
alpha channel, should the alpha be 1 or undefined.
From an app point of view, 1 probably makes more sense.
However, if the texture is in a RGBA format and there is garbage in
the A channel, it may be difficult for implementations to return 1.
An implementation may have to recompile the shader to force the alpha
channel to 1.
RESOLVED: alpha is defined to be 1 in this case.
9. How should the color conversion be described.
Options:
A) State that the color values are transformed to a linear colorspace
and represented as RGB values in that space. This may be difficult
for implementations since it may require nonlinear transformations
(e.g. gamma decoding). It is also problematic because usually many
more bits are required to represent a value in a linear colorspace
than in a gamma encoded colorspace.
B) State that the color is transformed to RGB but in the same
colorspace as the source image (i.e. no gamma encode or decode).
RESOLVED: Option B.
10. How does the implementation indicate which texture samplers and/or
texture units are not available when one or more external textures are
bound.
See discussion on GLES email list around Feb 23 with
subject "RE: [OpenGL-ES] IL/ES interaction: YUV texture extension
proposal"
Proposals:
A) The MAX_COMBINED_TEXTURE_IMAGE_UNITS,
MAX_VERTEX_TEXTURE_IMAGE_UNITS, and MAX_TEXTURE_IMAGE_UNITS parameters
change to reflect the current state.
B) New queries AVAILABLE_COMBINED_TEXTURE_IMAGE_UNITS,
AVAILABLE_VERTEX_TEXTURE_IMAGE_UNITS, and
AVAILABLE_TEXTURE_IMAGE_UNITS indicate current state, while
MAX_COMBINED_TEXTURE_IMAGE_UNITS, MAX_VERTEX_TEXTURE_IMAGE_UNITS, and
MAX_TEXTURE_IMAGE_UNITS remain constant and indicate the state when no
external textures are bound.
C) Query for number of required texture image units per texture
object. Draw calls fail with INVALID_OPERATION if the current
requirements for texture image units exceeds the number available.
RESOLVED: C
11. What happens when glUniform1i() sets a sampler to a value that is
larger than the number of available texture units?
NOTE: This issue no longer affects this extension. See issue 10 for
different issue related to texture *image* units.
This is really a GLES2 spec issue. See
khronos bug 3702
https://cvs.khronos.org/bugzilla/show_bug.cgi?id=3702
http://www.khronos.org/members/login/list_archives/arb-glsl/
0705/msg00010.html
http://www.khronos.org/members/login/list_archives/opengl_es/
0902/msg00148.html
RESOLVED: The issue is not resolved, but it no longer applies
directly to this extension. Further discussion should be in bug 3702.
12. What happens at draw time when the current state requires more texture
units than the implementation can support?
RESOLVED: The precedent, from (desktop) OpenGL, is to fail in
glValidate, and to fail in any draw call with an INVALID_OPERATION
error. Behavior described in this extension will match that
precedent.
13. How can this be conformance tested?
In the native code, add a function which takes as a
parameter an array of pixels. The function returns an EGLImage which
contains the pixels in some unspecified format. A test can call this
function, call glEGLImageTargetTexture2DOES() to associate it with an
external texture, and render using this texture, and read back the
framebuffer to confirm that the result is the expected result.
Note1: since the format is unknown and unknowable, possibly only the
high bit of each component (RGB) should be tested. It may be
sufficient to pass a single pixel (or single bit for each of R, G, an
B) and then create the EGLImage with every pixel in the image set to
that same value.
Note2: It might be a good idea to have an extra parameter, int index,
which allows the function to be implemented several different ways.
The test could be run several times, with index set to 0, 1, 2, ...
until the function returns EGL_NO_IMAGE. This way the function could
generate EGLImages with various formats. For example when index is 0
it could call OMX IL to generate a YUV planar EGLImage, when index is
1 it could call OMX AL to generate a YUV interleaved EGLImage, and
when index is 2 it could call into VG to generate an RGB EGLImage.
The meaning of each index would be up to the implementation. A simple
implementation might return an EGLImage when index=0 and return
EGL_NO_IMAGE otherwise.
Additional suggestion from Jon Leech:
The suggested conformance test in issue 13 is intentionally so vague
on precision (1 bit/component) that the conversion language seems even
less meaningful. The RGB bits that come out of texture sampling would
need have almost no relationship to what went in. ISTM the supplier of
the EGLImage knows the precision of it, and that information could be
provided to the test to put on tighter constraints.
RESOLVED: As described above.
14. Can the number of uniforms required by a shader change when switching
from one external texture to another, and therefore cause the shader
to fail? For example, imagine a program does this:
glLinkProgram(prog); // successful link
sampler = glGetUniformLocation(prog, "myExtSampler");
glUniform1i(sampler, 1);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_EXTERNAL, myTex1_rgb);
glDrawArrays(); // draw successfully
glBindTexture(GL_TEXTURE_EXTERNAL, myTex2_yuv);
glDrawArrays(); // Can this fail???
Is it acceptable for an implementation to fail the second
glDrawArrays() call because myTex2_yuv is a yuv image and requires
more uniforms to implement a color conversion matrix than myTex1_rgb
which is an rgb image and does not require any conversion matrix?
Note that this situation will only occur on implementation which will
recompile the shader based on the color conversion required.
Options:
A) No, the implementation is not allowed to fail. When the program is
linked the implementation must verify that there are enough uniforms
to implement the program for any flavor of external texture. If the
implementation does not provide enough uniforms for the program to
work with any external texture that the implementation supports, then
the implementation must fail at link time.
B) Yes, the implementation may fail in glDrawArrays or glDrawElements
if the number of uniforms required by the program exceeds those
available. This means that a call to glUniform1i() or glBindTexture()
can cause a shader program that used to work to stop working. (Note
that this is possible anyway since the new external texture may use
more texture image units than the old external texture (independent of
the number of uniforms). But that can be detected by the application
by querying REQUIRED_TEXTURE_IMAGE_UNITS_OES)
RESOLVED: choice B.
15. How should filtering of non-RGB formats be specified.
Options:
A) filtering occurs before transformation to RGB.
B) filtering occurs after transformation to RGB.
C) undefined (up to the implementation)
RESOLVED: C
Dependencies on EGL_OES_image_base and EGL 1.1
If either EGL 1.1 or the EGL_OES_image extension is not supported, all
discussion of EGLImages should be ignored, and any calls to
EGLImageTargetTexture2DOES should generate the error INVALID_OPERATION.
Dependencies on GL_OES_EGL_image
If GL_OES_EGL_image is supported then change the text in both extensions
to allow either TEXTURE_2D or TEXTURE_EXTERNAL_OES to be passed as the
<target> parameter to EGLImageTargetTexture2DOES(). When <target> is
TEXTURE_2D, behavior of EGLImageTargetTexture2DOES() is as described in
the GL_OES_EGL_image spec. When <target> is TEXTURE_EXTERNAL_OES,
behavior of EGLImageTargetTexture2DOES() is as described in this spec.
Revision History
#25 - (April 6, 2018) H1Gdev
Fix typo.
#24 - (April 23, 2015) Jon Leech)
- Fix typo EGLImageTargetTexImage2DOES -> EGLImageTargetTexture2DOES
(Bug 8114). Improve description of supported queries for new
tokens (Bug 8118).
#23 - (July 19, 2012) Acorn Pooley
- fix extension name from OES_EGL_image_external to
GL_OES_EGL_image_external
#22 - (Dec 17, 2010) Acorn Pooley
status to ratified.
#21 - (Sept. 29, 2010) Maurice Ribble
Update token numbers and updated status to approved.
#20 - (April 2, 2009) Acorn Pooley
Rename GL_OES_egl_image_external to GL_OES_EGL_image_external to be
consistant with GL_OES_EGL_image.
#19 - (March 31, 2009) Acorn Pooley
Minor fixes
#18 - (March 30, 2009) Acorn Pooley
Fix inconsistancy
#17 - (March 25, 2009) Acorn Pooley
Resolved issue 4 (and some others)
#16 - (March 16, 2009) Acorn Pooley
Augment issue 13
#15 - (March 13, 2009) Acorn Pooley
fix dependancy section
resolve issue 14 and fix text
#14 - (March 9, 2009) Acorn Pooley
Fix colorspace comments. Issue 9 is resolved.
#13 - (March 6, 2009) Acorn Pooley
Mark issue 6, 10, and 11 resolved.
Add issue 15.
#12 - (March 4, 2009) Acorn Pooley
Fix wording of uniform stuff.
#11 - (March 4, 2009) Acorn Pooley
Add issues 13, 14.
Add comments about extra uniforms required by external texture
samplers.
Allow external textures to work with default object 0.
Correct colorspace language.
#10 - (March 3, 2009) Acorn Pooley
Remove stale reference to MAX_TEXTURE_IMAGE_UNITS. Add fix to OpenGL
ES 2.0 section 2.10.5 (from bruce). Add contributors. Clarify
"texture unit" vs "texture image unit". Fix typos.
#9 - (February 26, 2009) Acorn Pooley
Clarify sync further. Add issue 12. Change "too many texture units"
behavior.
#8 - (February 26, 2009) Acorn Pooley
Clarify sync requirements (i.e. that EGLImage does not do sync)
#7 - (February 25, 2009) Acorn Pooley
Relax binding requirement - see issue 5
#6 - (February 25, 2009) Acorn Pooley
Add TEXTURE_BINDING_EXTERNAL_OES. Add texture state notes. Modify
colorspace conversion to be a linear function.
#5 - (February 24, 2009) Acorn Pooley
Disable GenerateMipmaps. Add issues 10 & 11.
#4 - (February 23, 2009) Acorn Pooley
Modify the "Texture Parameters" section in ES 1 and 2 specs
#3 - (February 20, 2009) Acorn Pooley
Clarify the reduction in number of texture units.
#2 - (February 20, 2009) Acorn Pooley
Fix some errors. replace textureExternal* sampler functions with
existing sampler2D* functions. Add issue 7,8,9. Fix spelling.
#1 - (February 9, 2009) Original draft