[Mesa-dev] [PATCH 1/2] glsl: always enable OES_standard_derivatives features if supported

[Ilia Mirkin]

On Wed, May 16, 2018 at 8:26 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
>
>
> On 16/05/18 22:09, Ilia Mirkin wrote:
>>
>> On Wed, May 16, 2018 at 8:04 AM, Timothy Arceri <tarceri at itsqueeze.com>
>> wrote:
>>>
>>>
>>>
>>> On 16/05/18 21:12, Ilia Mirkin wrote:
>>>>
>>>>
>>>>   From the spec,
>>>>
>>>> """
>>>>       The built-in derivative functions dFdx, dFdy, and fwidth are
>>>> optional, and
>>>>       must be enabled by
>>>>
>>>>       #extension GL_OES_standard_derivatives : enable
>>>>
>>>>       before being used.
>>>> """
>>>>
>>>> Sounds like you need an application override?
>>>
>>>
>>>
>>> The ES spec has no such wording is simply states:
>>>
>>> "dFdx(), dFdy(), and fwidth() are made optional."
>>
>>
>> That is under the heading of "Changes from Revision 59 of the OpenGL
>> Shading Language specification:", i.e. desktop GLSL.
>>
>> There isn't a single other reference to those functions anywhere else
>> in https://www.khronos.org/files/opengles_shading_language.pdf . The
>> "optional" is in reference to it being moved out to an extension
>> rather than being part of the core language.
>
>
> It also says noise is optional but there is no spec for it that I can see.

Yeah, the function just doesn't exist in ES. Those comments sections
at the top of "how does this differ from X" aren't normative. Look at
the list of functions -- is it in there? If not, it doesn't exist.

  -ilia