EXT_EGL_image_external_wrap_modes

GL_EXT_EGL_image_external_wrap_modes

Jeff Leger, Qualcomm
Rob VanReenen, Qualcomm
Jonathan Wicks, Qualcomm
John Carmack, Oculus
Cass Everitt, Oculus
Graeme Leese, Broadcom

Jeff Leger, Qualcomm  (jleger 'at' qti.qualcomm.com)

Complete

Last Modified Date: Feb 06, 2018
Revision: #4

OpenGL ES Extension #298

Requires OES_EGL_image_external.

Interacts with OES_EGL_image_external_essl3.

OES_texture_border_clamp affects the definition of this extension.

The portions of this extension that modify/extend 
OES_EGL_image_external are written against OpenGL ES 2.0.
The portions of this extension that modify/extend 
OES_texture_border_clamp are written against OpenGL ES 3.0.
The portions of this extension that modify/extend OES_EGL_image_external_essl3 are
written against OpenGL ES 3.0.

This extension builds on OES_EGL_image_external, which only allows
a external images to use a single clamping wrap mode:  CLAMP_TO_EDGE.
This extension relaxes that restriction, allowing wrap modes REPEAT
and MIRRORED_REPEAT.  If OES_texture_border_clamp is supported, then 
CLAMP_TO_BORDER is also allowed.

This extension similarly adds to the capabilities of OES_EGL_image_external_essl3,
allowing the same additional wrap modes.

Since external images can be non-RGB, this extension clarifies how
border color values are specified for non-RGB external images.

No known IP claims.

None.

None.

 None.

Modify the fourth sentence of the first paragraph of Section 3.7.14,
as added by OES_EGL_image_external

from:
     "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."
to:
    [[ The following applies if OES_texture_border_clamp is not supported. ]]

    "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 value other than
    CLAMP_TO_EDGE, REPEAT, or MIRRORED_REPEAT."

    [[ The following applies if OES_texture_border_clamp is supported. ]]

    "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 value other than
    CLAMP_TO_EDGE, REPEAT, MIRRORED_REPEAT, or CLAMP_TO_BORDER."

[[ The following applies if OES_texture_border_clamp is supported. ]]

Add the following paragraph to the end of Section 3.7.14, as added
by OES_EGL_image_external:

    The state TEXTURE_BORDER_COLOR_OES is specified as an RGBA color
    in linear color space.  For example, if the original image is stored
    in(non-linear) ITU-R Rec. 601 YV12, the TEXTURE_BORDER_COLOR_OES
    must still be specified as an RGBA color in linear color space.

Modify the paragraph as added by OES_EGL_image_external

from:
        "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."
to:
    [[ The following applies if OES_texture_border_clamp is not supported. ]]

        "When <target> is TEXTURE_EXTERNAL_OES only NEAREST and
    LINEAR are accepted as TEXTURE_MIN_FILTER and only CLAMP_TO_EDGE,
    REPEAT, or MIRRORED_REPEAT are accepted as TEXTURE_WRAP_S and
    TEXTURE_WRAP_T."

    [[ The following applies if OES_texture_border_clamp is supported. ]]

        "When <target> is TEXTURE_EXTERNAL_OES only NEAREST and
    LINEAR are accepted as TEXTURE_MIN_FILTER and only CLAMP_TO_EDGE,
    REPEAT, MIRRORED_REPEAT, or CLAMP_TO_BORDER are accepted as 
    TEXTURE_WRAP_S and TEXTURE_WRAP_T."

Modify the sentence added by OES_texture_border_clamp

From:
    "If the texture contains color components, the values of 
    TEXTURE_BORDER_COLOR_OES are interpreted as an RGBA color to 
    match the texture's internal format in a manner consistent with
    table 3.11."

To:
     "If the texture contains color components, the values of
    TEXTURE_BORDER_COLOR_OES are interpreted as an RGBA color in
    linear color space to match the texture's internal format in a
    manner consistent with table 3.11, except that if an external
    texture stores YUV values then the linear RGBA border value is
    first converted into a YUVA value in the colorspace of the
    texture."

Modify the the following sentence added by OES_EGL_image_external_essl3

From:
    "For example, if TEXTURE_WRAP_S or TEXTURE_WRAP_T is set to
     anything but CLAMP_TO_EDGE on the sampler object bound to a
     texture unit and the texture bound to that unit is an external
     texture, the texture will be considered incomplete."

To:

    [[ The following applies if OES_texture_border_clamp is not supported. ]]

     "For example, if TEXTURE_WRAP_S or TEXTURE_WRAP_T is set to
      anything but CLAMP_TO_EDGE, REPEAT, or MIRRORED_REPEAT on the
      sampler object bound to a texture unit and the texture bound
      to that unit is an external texture, the texture will be
      considered incomplete."

    [[ The following applies if OES_texture_border_clamp is supported. ]]

     "For example, if TEXTURE_WRAP_S or TEXTURE_WRAP_T is set to
      anything but CLAMP_TO_EDGE, REPEAT, MIRRORED_REPEAT, or
      CLAMP_TO_BORDER on the sampler object bound to a texture unit
      and the texture bound to that unit is an external texture,
      the texture will be considered incomplete."

1) For YUV texture formats, should the should the border color be 
specified as RGBA or YUVA ?

Resolved:  The border color should be specified as linear RGBA since the 
application may not know the underlying texture format/colorspace.  The 
color should be converted by the implementation to a colorspace (e.g., 
ITU-R Rec. 601) matching the texture's internal format.

Rev.    Date     Author    Changes
----  --------  --------  ----------------------------------------------
 1    12/19/17   jwicks    Initial spec
 2.   01/03/18   jleger    Updates and cleanup.
 3.   01/05/18   jleger    Allow additional wrap modes.  Rename the extension.
 4.   02/06/18   jleger    Added interactions with OES_EGL_image_external_essl3.