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Re: feTurbulence with filter primitive subregions

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 12 May 2008 10:10:44 -0700
Message-ID: <11e306600805121010x496a0a5dy378d4303f4e76dc@mail.gmail.com>
To: "Erik Dahlström" <ed@opera.com>
Cc: www-svg <www-svg@w3.org>
On Mon, May 12, 2008 at 5:31 AM, Erik Dahlström <ed@opera.com> wrote:

> On Sun, 11 May 2008 09:24:01 +0200, Robert O'Callahan <
> robert@ocallahan.org> wrote:
>
>  It's not clear to me from the spec what the 'point' parameter of the
> > 'turbulence' function means.
> >
> > Suppose I have
> > <filter primitiveUnits="userSpaceOnUse" x="0" y="0" width="20"
> > height="20">
> >  <feTurbulence x="10" y="10" width="10" height="10"/>
> > </filter>
> >
> > When we compute 'turbulence' for the top-left corner of the feTurbulence
> > filter primitive subregion, what is 'point'? I assume it's either (0,0)
> > or (0.5,0,5).
> >
>
> I think that should depend on how an implemention does sampling in
> general. It's unlikely that an error would be easy to spot in most cases
> though.
>

'point' values range from 0 to 1, don't they? So you'd get a completely
different image depending on whether you interpret the turbulence as filling
the filter region and being clipped to the filter primitive subregion, or
just filling the filter primitive subregion.

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]
Received on Monday, 12 May 2008 17:11:31 GMT

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