"dlm" <me### [at] addressinvalid> wrote:
> "Grassblade" <nomail@nomail> wrote in message
> news:web.471f9b31e04cdb41654d6f060@news.povray.org...
> >I used the SDL raytracer found in the help file
> > (http://www.povray.org/documentation/view/3.6.1/123/) to refine an idea
> > more or less suggested by Bruno Cabasson.
> > Top picture skips a ray if (square of) distance in colour-space is smaller
> > than an user supplied threshold.
> > Middle pic is the result of the unadulterated SDL raytracer.
> > Bottom pic is the difference of the two.
> > The supplied Skip-a-ray pic requires about 65-70% of the time to render.
> >
>
> Neat.
> I would be hard-pressed to tell the difference.
> So the slight differences all show up at the edges.
> Presumably these are glancing rays?
> So this is effectively like shifting gear on AA, with jaggies showing up at
> some edges.
> DLM

That's a good question, jaggies shouldn't show up in principle, because of
the threshold. Yet the difference picture shows the outline of at least the
two bottom spheres. I'm not entirely sure where it comes from. Maybe if I
rendered with no AA it would go away. Or maybe I need a lower threshold,
but then render-time might go up.
And, yes, the algorithm acts like a sort of AA, but with different weights
from what we are used to.

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