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Re: SVG 1.2 Comment: vector effects

From: Philippe Lhoste <PhiLho@GMX.net>
Date: Thu, 11 Nov 2004 11:04:43 +0100
Message-ID: <4193393B.6090504@GMX.net>
CC: www-svg@w3.org

Ian Hickson wrote:
>> As a content creator and cartographer I can only second Peters and Dougs 
>> comments. Many of the more complex map symbolization problems can be 
>> adressed using vector effects. [...]
>> 
>> Besides that, vector effects can help to solve quite a few GIS analysis
>> features (such as intersection, excluding, merging of elements). Doing it all
>> by script would be complex and slow, besides the problems that Doug mentioned,
>> regarding semantics.
> 
> I don't really see that it is appropriate for the Web browser to have 
> built-in support for GIS analysis. I don't doubt that it would be very 
> useful in your domain, but there is a line to be drawn at how much a Web 
> browser needs to support.
[snip]
> So yes; simple things like keeping the strokes the same width despite 
> zooming seem like they could be cheaply supported in SVG. More complicated 
> things such as client-side fill intersections, unions, etc, seem excessive 
> for a Web UA.

I don't agree here. "intersection, excluding, merging of elements" isn't 
limited to GIS use, but are really useful for generic graphic use.

See PoV-Ray's "Constructive Solid Geometry" (also known as CSG) for 
example (it is 3D, but in the same spirit).

Indeed, these effects can be done with an authoring tool, but many SVG 
files are still done by hand, and such effects will ease greatly the 
coding of some images (if simple to understand and use...).

Side note on a remark of you about reproductability of text on path. You 
discarded this, stating it is not important, that UA just have to do its 
best and the final rendering will come as it goes.
Sorry if I mis-paraphrase you from memory...

OK, exact wording is:
-----
 >> glyphs should be placed, but Adobe and others explained that there are
 >> other, more sophisticated algorithms for laying out text along a path.

That's another good example of where the exact algorithm used should,
IMHO, be left up to the UA
-----

I do believe that exact positionning is important. I did a SVG rendition 
of the Lua logo <http://www.lua.org> with text ("the programming 
language") is going on an arc from 190 to 59. I would hate to see on 
another viewer that text overlaps with the circle after the text, just 
because of the use of another algorithm... (assuming that end user have 
the proper font, of course, but it is a common Helvetica).

You can object that I have just to use the right transforms on each 
letter to get such precision, but the point of text on path is right to 
avoid such lengths, to preserve text as text, not as a bunch of letters, 
and to avoid using an authoring tool to get such effects.

Otherwise, one could have reduced the set of SVG shapes to only path, as 
it is enought for all needs.

-- 
Philippe Lhoste
--  (near) Paris -- France
--  Professional programmer and amateur artist
--  http://Phi.Lho.free.fr
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Received on Thursday, 11 November 2004 10:06:54 UTC

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