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Re: [Public WebGL] WEBGL extension suggestion: EXT_shader_framebuffer_fetch



Hi Ashley,

I don't think there is an overlap between the extensions because
developers using each extension will not be getting the same thing:

- The WEBGL_blend_equation_advanced_coherent extension provides
developers with an extended range of blend modes.
- The EXT_shader_framebuffer_fetch extension provides an extra
built-in fragment shader input.

Providing developers with an extended range of blend modes can be (and
probably should be) implemented in several different ways depending on
the GPU architecture - one way, if a GPU supports the
EXT_shader_framebuffer_fetch extension, is to make use of the
gl_LastFragData[] extra built-in fragment shader input - but the
WEBGL_blend_equation_advanced_coherent extension isn't actually
dependent on the EXT_shader_framebuffer_fetch extension.

And what can be done with the extra built-in fragment shader input, on
GPU architectures that support the EXT_shader_framebuffer_fetch
extension, isn't limited to extra blend modes - so it wouldn't be
ideal to limit developers who wish to use the
EXT_shader_framebuffer_fetch extension.

Cheers,
Ray.

On Fri, May 15, 2020 at 12:38 PM Ashley Gullen (ashley@scirra.com)
<public_webgl@khronos.org> wrote:
>
> Out of curiosity, is this extension intended for implementing different kinds of blending in shaders? Is there any overlap with WEBGL_blend_equation_advanced_coherent? (Draft: https://www.khronos.org/registry/webgl/extensions/WEBGL_blend_equation_advanced_coherent/ - no implementations yet AFAIK)
>
>
> On Fri, 15 May 2020 at 11:20, Ray Tran (ray.tran@snapchat.com) <public_webgl@khronos.org> wrote:
>>
>> Hi Ken,
>>
>> Thanks for the reply - the pull request is here: https://github.com/KhronosGroup/WebGL/pull/3074
>>
>> Do let me know if any changes need to be made to the proposal?
>>
>> Cheers,
>> Ray.
>>
>>
>>
>> On Mon, May 11, 2020 at 11:01 PM Ken Russell (kbr@google.com) <public_webgl@khronos.org> wrote:
>>>
>>> Hi Ray,
>>>
>>> Yes, a high-impact but mostly mobile-only extension like this can certainly be considered. Would you please take a little time and put up a pull request on https://github.com/KhronosGroup/WebGL under https://github.com/KhronosGroup/WebGL/tree/master/extensions/proposals, following the XML pattern there?
>>>
>>> Thanks,
>>>
>>> -Ken
>>>
>>>
>>>
>>> On Mon, May 11, 2020 at 10:05 AM Mark Callow (khronos@callow.im) <public_webgl@khronos.org> wrote:
>>>>
>>>>
>>>>
>>>> On May 11, 2020, at 9:50, Ray Tran (ray.tran@snapchat.com) <public_webgl@khronos.org> wrote:
>>>>
>>>>  I have also found that
>>>> major mobile GPU vendors have supported and advised developers to use
>>>> this extension to improve performance on their GPUs for many (5+)
>>>> years.
>>>>
>>>>
>>>> This is ironic given the opposition to adding programmable blending to OpenGL over many, many years, decades even, on the grounds that it would cause performance issues.
>>>>
>>>> Regards
>>>>
>>>>     -Mark
>>>>
>>>
>>>
>>> --
>>> I support flexible work schedules, and I’m sending this email now because it is within the hours I’m working today.  Please do not feel obliged to reply straight away - I understand that you will reply during the hours you work, which may not match mine.
>>>

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