W3C home > Mailing lists > Public > www-style@w3.org > October 2011

Re: [css-shaders] Feedback about default fragment shader in CSS shaders proposal

From: Chris Marrin <cmarrin@apple.com>
Date: Thu, 20 Oct 2011 10:52:59 -0700
Cc: vhardy@adobe.com, www-style@w3.org, public-fx@w3.org
Message-id: <E235D5F3-F8CA-4CFF-8A37-D2A79034E2D3@apple.com>
To: noam.rosenthal@nokia.com

On Oct 20, 2011, at 8:24 AM, noam.rosenthal@nokia.com wrote:

> 
>> [vh] I agree that we should not have default uniforms and let people define their shaders if they need that. I have added an issue about turning blending on:
> 
> We do have a default uniform for the projection matrix… 
> Re. opacity, people can't do that in their shader, because specifically the opacity and transform parameters come from the "system" and not from the animated shader properties themselves; that's because those are the two parameters that are accumulated with the opacity and transform of the ancestors in the layer tree.
> 
> Having said that, I think we can work without it, it just means that we'd have to use an FBO for opacity on a css-shaded element, something we could otherwise potentially avoid.

Ok, I've gotten myself more confused now (as Siri would say "it's not you, it's me"). As I said in my latest post on blending modes, I don't think we need to do blending of the filtered element. So it seems like what we're discussing here is having some way to tell the rendering backend if this filtered element will have any non-opaque pixels. Whether we have a "standard" opacity uniform or not, the author can still write a fragment with a non-opaque alpha value. So there're no a priori way to know if you need to blend the element, is there? Or have I missed the point again?

-----
~Chris
cmarrin@apple.com
Received on Thursday, 20 October 2011 17:53:29 GMT

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