EXT_pixel_format_float

EGL_EXT_pixel_format_float

Tom Cooksey
Jesse Hall
Mathias Heyer
Adam Jackson
James Jones
Daniel Koch
Jeff Leger
Weiwan Liu
Jeff Vigil

Weiwan Liu, NVIDIA (weiwliu 'at' nvidia.com)

Complete

Version 4 - Nov 22, 2016

EGL Extension #106

This extension is written against the wording of the EGL 1.5 specification
(August 27, 2014).

This extensions aims to provide similar functionality as GL_ARB_color_-
buffer_float, WGL_ARB_pixel_format_float and GLX_ARB_fbconfig_float. This
extension allows exposing new EGLConfigs that support formats with
floating-point RGBA components. This is done by introducing a new EGLConfig
attribute that represents the component type, i.e. fixed-point or
floating-point. Such new EGLConfigs can be used to create floating-point
rendering surfaces and contexts.

None

None

Accepted as an attribute name in the <attrib_list> argument of
eglChooseConfig, and the <attribute> argument of eglGetConfigAttrib:

    EGL_COLOR_COMPONENT_TYPE_EXT              0x3339

Accepted as attribute values for the EGL_COLOR_COMPONENT_TYPE_EXT attribute
of eglChooseConfig:

    EGL_COLOR_COMPONENT_TYPE_FIXED_EXT        0x333A
    EGL_COLOR_COMPONENT_TYPE_FLOAT_EXT        0x333B

Additions to table 3.1, "EGLConfig attributes" in Section 3.4 "Configuration
Management":

    Attribute                       Type       Notes
    ---------                       ----       ---------
    EGL_COLOR_COMPONENT_TYPE_EXT     enum       color component type

Append one paragraph at the end of "The Color Buffer" section on page 21:

    EGL_COLOR_COMPONENT_TYPE_EXT indicates the color buffer component type,
    and must be either EGL_COLOR_COMPONENT_TYPE_FIXED_EXT for fixed-point
    color buffers, or EGL_COLOR_COMPONENT_TYPE_FLOAT_EXT for floating-point
    color buffers.

Add one entry to Table 3.4 and increment "Sort Priority" between "2" and
"11" by one for existing entries:

    Attribute                      Default
    -----------                    ------------
    EGL_COLOR_COMPONENT_TYPE_EXT    EGL_COLOR_COMPONENT_TYPE_FIXED_EXT

    Selection Criteria    Sort Order    Priority
    ------------------    ----------    --------
    Exact                 Special        2

Insert before the entry for EGL_COLOR_BUFFER_TYPE, and increment its
numbering and subsequent numbering by one:

    2. Special: by EGL_COLOR_COMPONENT_TYPE_EXT where the precedence is
    EGL_COLOR_COMPONENT_TYPE_FIXED_EXT, EGL_COLOR_COMPONENT_TYPE_FLOAT_EXT

Change footnote 8 on page 30 to:

    Within the same EGL_COLOR_COMPONENT_TYPE_EXT, this rule places configs
    with deeper color buffers first in the list returned by
    eglChooseConfig...

1. When reading from or rendering to a floating-point EGL surface, is there
   any clamping performed on the values?

   RESOLVED: It depends on the behavior of the client API. For example, in
   OpenGL and ES, by default no clamping will be done on the floating-point
   values, unless the clamping behavior is changed via the client API.

2. When rendering to a floating-point EGL surface, since values may not be
   clamped to [0, 1], what is the range of values that applications can use
   to get display's "darkest black" and "brightest white"?

   RESOLVED: It is not in the scope of this extension to define a range of
   values that corresponds to display's capability. Please refer to the EGL
   specification for the chosen colorspace (EGL_GL_COLORSPACE), where such a
   reference range may be defined.

Rev.     Date        Author          Changes
----   --------  ---------------  ------------------------------------------
 1     12/11/15   Weiwan Liu      Initial version
 2     05/18/16   Weiwan Liu      Rename to EXT
 3     05/31/16   Weiwan Liu      Add issues
 4     11/22/16   Weiwan Liu      Change status to complete