[cairo] Avoiding seams
eh-cairo at narthex.us
Mon Dec 12 20:01:02 PST 2005
I can't address everything yet, because I'm still investigating, but
I can respond to one point.
>On Mon, 2005-12-12 at 18:19 -0700, Eric Hughes wrote:
> > Anti-aliasing can be done locally with path-as-boundary, with one
> > caveat. You can draw either with luminosity (additive) or occlusion
> > (subtractive). As long as one or the other is specified, you can get
> > a linear behavior at edges.
At 07:21 PM 12/12/2005, MenTaLguY wrote:
>There is a fundamental ambiguity:
The fundamental ambiguity of this example is because of the use of
simple opaque occlusion, what is called there the "covered-by"
operator. Mathematically, this is the function max(), which isn't
linear over the integers. If you have a non-linear compositing
operator, then you're in a situation where computing an alias filter
independently per element doesn't work. You have to have linearity
to be able to compute the filter function independently per element.
If you need a non-linear compositing operator to deal with vector
graphics, you still don't need to compute it over the whole
screen. Doing it at intersections (including collinear edges and
coincident vertices) suffices.
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