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RE: Comments on SVG 2 Gradients

From: Cyril Concolato <Cyril.Concolato@cisra.canon.com.au>
Date: Fri, 9 Dec 2011 03:21:55 +0000
To: "SVG WG (public-svg-wg@w3.org)" <public-svg-wg@w3.org>
Message-ID: <54EF1DA3171CEE48AD59D7FF0DE043C3D5CB8F@exm01-wvp.cisra.canon.com.au>
Hi all,

As per ACTION-3184, I've updated the Advanced Gradient Requirements document [1] to include the requirement about having smooth gradients across points/patches. I also added the other type of gradient mentioned in the Microsoft paper.


[1] http://dev.w3.org/SVG/modules/advancedgradients/SVGAdvancedGradientReqs.html

-----Original Message-----
From: Tab Atkins Jr. [mailto:jackalmage@gmail.com]
Sent: Friday, 9 December 2011 8:53 AM
To: Tavmjong Bah
Cc: Cyril Concolato; SVG WG (public-svg-wg@w3.org)
Subject: Re: Comments on SVG 2 Gradients

On Thu, Dec 8, 2011 at 11:27 AM, Tavmjong Bah <tavmjong@free.fr> wrote:
> On Thu, 2011-12-08 at 05:47 +0000, Cyril Concolato wrote:
>> The next item to be discussed on the SVG 2 Requirements list is
>> Gradients. I’ve a made a small page
>> (http://www.w3.org/Graphics/SVG/WG/wiki/SVG2GradientsComments)
>> describing some comments that I would like to discuss, possibly if we
>> have time during the next telcon. Let me know if you have comments.
>        I've seen the same problem you point out with some of the
> drawings I've made. It shows up when one has a large change in color
> as your black and white example shows. The problem can also be seen
> with the existing SVG linear and radial gradients. I've been planning
> on adding tensor meshes to my version of Inkscape to see if moving the
> tensor handles can minimize the effect.
>        You point out the problem can be seen to some extent with my
> color conical gradient example. This is the exact same problem as one
> has with linear and radial gradients. I verified this when I first saw
> the problem and wanted to know if it was a bug in the Cairo
> implementation or if it was inherent to linear/radial/Coons patch mesh gradients.
>        The paper you refer to is interesting, especially the mesh
> optimization part (from Inkscape's point of view). However, I wonder
> in practice if the drawings would appear much different if the meshes
> were simply Coons Patch meshes. For the most part, all the meshes have
> small changes in color where the problem you've pointed out would not be so apparent.
>        For me, the question becomes: do we want to specify the more
> complicated Ferguson meshes (or something similar) in the SVG spec or
> stay with the more simpler (and "standard") Coons Patch/Tensor Patch
> meshes and let the authoring software take care of any problems (like
> Illustrator does when exporting to PDF).

The most important consideration from my perspective is what can be efficiently implemented in browsers and in GPUs.  A slow gradient will kill performance on the whole page.  So, whatever the prettiest thing that can still be efficiently implemented is what we should go with.

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Received on Friday, 9 December 2011 03:22:34 UTC

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