W3C home > Mailing lists > Public > www-svg@w3.org > February 2012

Re: New version of mesh branch.

From: Tavmjong Bah <tavmjong@free.fr>
Date: Mon, 06 Feb 2012 21:12:19 +0100
Message-ID: <1328559139.2004.21.camel@LeLion>
To: Rik Cabanier <cabanier@gmail.com>
Cc: Israel Eisenberg <owlgems@yahoo.com>, Cyril Concolato <Cyril.Concolato@cisra.canon.com.au>, www-svg <www-svg@w3.org>

Hi all,

I apologize for not replying inline... me email client is making a mess
of the various quote styles in the last email.

@Rik: Yes, the question is how does Illustrator calculates the
colors/control points of the hidden patches.

@Rik: I don't mean ICC profile. I mean the change in a color's magnitude
across the patch.

@Israel: In your test at
http://owl3d.com/tests/Gradient_Mesh/lerpHermite.html , try putting in
the  values [[0,0,0][127,127,127][255,255,255]]. The resulting gradient
has visual artifacts. In this case you don't want the derivative to be
zero at the border. You do want the derivative to be the same on both
sides and these derivatives may be different for the different colors.

I find the keySpline idea interesting as this allows any slope at the
edge (but you would still have problems of needing to match slopes of
three different colors). I am not sure how you would paint an arbitrary
shaped patch. The Cairo rendering library algorithm of dividing a patch
horizontally into patches that have a width of no greater than one pixel
and then painting each of those patches as a Bezier line would need to
be modified in a non-trivial way. For export to PostScript/PDF one could
subdivide the patch as is done by Illustrator and export type 6 or 7

Received on Monday, 6 February 2012 20:12:51 UTC

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