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Re: [filters] Shading language recommendation

From: Dirk Schulze <dschulze@adobe.com>
Date: Wed, 22 Aug 2012 13:58:21 -0700
To: Sylvain Galineau <sylvaing@microsoft.com>
CC: Chris Marrin <cmarrin@apple.com>, "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <DA870B12-A465-407B-9FC3-BB972948C021@adobe.com>
Hi Sylvain,

On Aug 22, 2012, at 11:00 AM, Sylvain Galineau <sylvaing@microsoft.com> wrote:

> [Chris Marrin:]
> 
> 
>>> I would like to resolve this before FPWD.
> 
>> I'd like to return to the questions put forth in previous posts:
> 
>> 1) Is your objection technical or something else?
> 
> 1) We believe the conformance of a Filter Effects implementation should not depend on its use of GL SL ES i.e. if a UA wants to support this functionality with a different technology they should be able to do so.
Yes, I agree. And it is possible like shown with ANGLE. 

> 2) Generally speaking, we do not believe a CSS feature should require, recommend or depend on a specific low-level technology such as a shading language. We are not aware of any such dependencies to date and believe such architectural concerns should be kept orthogonal. As CSS specifications generally avoid even taking a dependency on a specific document language it is very unusual for a module to recommend a technology which, from a CSS standpoint, has been an implementation detail to date. A clear compelling reason to do so should at least be explicitly articulated in the specification. 
GLSL is a shading langage. But it does not mean that it is a low-level technology or relies on low level technologies. ANGLE is one project that aims to parse and translate GLSL.

> 3) More specifically, if the feature aims to provide an entry point to lower level capabilities for extensibility purposes e.g. custom CSS shaders, we believe there should be a mechanism to support alternative languages; this would also future-proof the platform.
The specification has a section that mentions various possible (and considered) shading languages. We choose GLSL over others, since WebGL is widely implemented and exposed to browsers. A lot of developers are already familiar with GLSL. There is nothing similar available for the web at the moment. In general I am not opposed to more shading languages, but a default, required language seems to be in the interest of web developers.

> 4) We are concerned that including GL SL as a RECOMMENDED feature makes it an essential feature under the W3C Patent Policy. We don't believe the shading language itself is within the scope of the CSS WG charter and we didn't carry out the  comprehensive IP review that would be necessary for us to participate on that basis. We suspect that other organizations also didn't do this.
We were about to publish a FPWD. Every member of the W3C has three weeks to verify if own patents are affected and if it wants to object if they are.

> I would like to resolve this before FPWD.

The SVG WG and the CSS WG agreed to publish a FPWD of Filter Effects. If you object to the decisions of the WGs now, it is necessary to request a resolution from the WGs to not publish FPWD.

Greetings,
Dirk

> 
> 
>> 2) If your objection is based on the issue of "my platform does not support GLSL", what about ANGLE and the fact that 
>> WebGL (which is the basis for the shading language specified) is designed to be implemented on Direct3D, and in fact 
>> there are currently multiple such implementations available?
> 
> See above.
> 
>> 3) If the spec were written with no recommended shading language, wouldn't that inhibit widespread adoption? 
>> How would we deal with that?
> 
> The widespread adoption of what? Do canned effects such as grayscale, sepia, saturate etc. need a specific shading
> language recommendation to achieve interop? 
> 
> 
Received on Wednesday, 22 August 2012 20:58:54 GMT

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