Re: [css-shaders] CSS shaders for custom filters (ACTION-3072)


Sorry for the late response, I was at a conference. Responding to Robert
but after reading the whole thread.

To the question about the effect of shaders on input that goes through
filters, Dean provided the answer I would have given. This is an issue the
group has discussed even before shaders, because it exists regardless of
shaders. Shaders may make things more complex (e.g., points may be moved
in a 3D space and obscure each other before being projected back in 2D
space) but the core issue is the same. Dean mentioned he had an action on
this and I am happy to work with him on it if he would like to collaborate
on a proposal. The reason this is not discussed in the proposal is because
it is not a new issue for filter effects, but may be the proposal should
have said so.

Regarding the APIs for converting points from one element's coordinate
system to another, I would have to think about this more. Thinking about
it a bit, there seem that we have to consider both the vertex shader
effect and the fragment or regular filter effect. I think both can
introduce difficulties for this coordinate transform API (I am thinking,
in particular, of filters such as feFlood or feTurbulence, and filters
that do 3D warping).

Kind regards,

From:  Robert O'Callahan <>
Reply-To:  "" <>
Date:  Tue, 4 Oct 2011 18:48:51 -0700
To:  Adobe Systems <>
Cc:  " CSS" <>, ""
<>, SVG WG <>
Subject:  Re: [css-shaders] CSS shaders for custom filters (ACTION-3072)

>Up until now filters haven't affected the processing of input events,
>mainly because filters weren't really designed to modify geometry, but
>now it seems to me that input events should be affected by the vertex
>shader so that the event is delivered to the element it appears to be
>over. In most of your demos, I think this behavior would be expected and
>any other behavior would be wrong.
>This would add to the desire that we be able to run the vertex shaders
>easily on the CPU.
>A related question is whether and how filters with vertex shaders should
>affect any proposed APIs for converting points and quads from the
>coordinate system of one element to another. Should those APIs take into
>account the effects of vertex shaders?
>"If we claim to be without sin, we deceive ourselves and the truth is not
>in us. If we confess our sins, he is faithful and just and will forgive
>us our sins and purify us from all unrighteousness. If we claim we have
>not sinned, we make him out to be a liar and his word is not in us." [1
>John 1:8-10]

Received on Wednesday, 5 October 2011 19:39:06 UTC