NV_coverage_sample_resolve

EGL_NV_coverage_sample_resolve

James Jones, NVIDIA Corporation (jajones 'at' nvidia.com)

Copyright NVIDIA Corporation, 2011

NVIDIA Proprietary

Last Modified Date:  2011/04/13
NVIDIA Revision: 1.0

EGL Extension #30

Written based on the wording of the EGL 1.4 specification.

Trivially interacts with EGL_NV_coverage_sample

Requires EGL 1.2.

NV_coverage_sample introduced a method to improve rendering quality
using a separate buffer to store coverage information for pixels in
the color buffers.  It also provided a mechanism to disable writing
to the coverage buffer when coverage sample filtering was not needed
or undesirable.  However, it did not provide a way to disable
reading data from the coverage buffer at resolve time.  In some
cases performance can be improved by eliminating these memory reads.
To that end, this extension exposes a surface attribute that allows
applications to specify when no coverage sample resolve is desired.

NVIDIA Proprietary

None

None

Accepted by the <attribute> parameter of eglSurfaceAttrib and
eglQuerySurface:

    EGL_COVERAGE_SAMPLE_RESOLVE_NV              0x3131

Accepted by the <value> parameter of eglSurfaceAttrib and returned
in the <value> parameter of eglQuerySurface when <attribute> is
EGL_COVERAGE_SAMPLE_RESOLVE_NV:

    EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV      0x3132
    EGL_COVERAGE_SAMPLE_RESOLVE_NONE_NV         0x3133

Additions to section 3.5.6 (Surface Attributes)

Replace the last sentence of paragraph 2 (p. 35):

"Attributes that can be specified are
EGL_COVERAGE_SAMPLE_RESOLVE_NV, EGL_MIPMAP_LEVEL,
EGL_MULTISAMPLE_RESOLVE, and EGL_SWAP_BEHAVIOR."

Add the following paragraphs between paragraphs 2 and 3 (p. 35):

"If <attribute> is EGL_COVERAGE_SAMPLE_RESOLVE_NV, then <value>
specifies the filter to use when resolving the coverage sample
buffer.  A <value> of EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV chooses
the default implementation-defined filtering method, while
EGL_MULTISAMPLE_RESOLVE_NONE_NV disables filtering based on coverage
data.

"The initial value of EGL_COVERAGE_SAMPLE_RESOLVE_NV is
EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV."

Add the following paragraph after paragraph 13 (p. 36):

"Querying EGL_COVERAGE_SAMPLE_RESOLVE_NV returns the filtering
method used when performing coverage buffer resolution.  The filter
may be either EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV or
EGL_COVERAGE_SAMPLE_RESOLVE_NONE_NV, as described above for
eglSurfaceAttrib."

This extension relies on language in EGL_NV_coverage_sample to
describe the coverage sample buffer.

If EGL_NV_coverage_sample is not present, this extension has no
effect on rendering.

1.  Should it be an error to set EGL_COVERAGE_SAMPLE_RESOLVE_NV on
    surfaces that don't have a coverage buffer?

    RESOLVED:  No.  EGL_COVERAGE_SAMPLE_RESOLVE_DEFAULT_NV will behave
    the same as EGL_COVERAGE_SAMPLE_RESOLVE_NONE_NV in this case.

- Initial revision.