Re: New version of mesh branch.

On Mon, Feb 6, 2012 at 12:12 PM, Tavmjong Bah <tavmjong@free.fr> wrote:

>
> Hi all,
>
> I apologize for not replying inline... me email client is making a mess
> of the various quote styles in the last email.
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> @Rik: Yes, the question is how does Illustrator calculates the
> colors/control points of the hidden patches.
>

I think it simply subdivides the patch. It's easy to create new control
points (just split the beziers) and to calculate their color.
By subidviding, I believe the mesh becomes smoother.


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

speaking of color, do you use sRGB or linearRGB to create the mesh?


>
> @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
> patches.
>
>                                        Tav
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