Alain <ele### [at] netscapenet> wrote:
> Mike nous illumina en ce 2008-10-13 13:37 -->
> > Actually, I just tried it with photons on and it did not get rid of the
> > speckles.  Also, I do not think the speckles are from the egg crate pattern
> > since the frequency is too small and since this program does not seem to take
> > into account interference of waves, I don't think it would be possible to have
> > such a small frequency developing.  The reason I am being such a stickler with
> > this is that I plan on using this for visualizing an experiment and we would at
> > least try to minimize artifacts as much as possible.
> >
> > -Mike
> >
> >
> >
> >
> > "Cousin Ricky" <ric### [at] yahoocom> wrote:
> >> "Mike" <win### [at] hotmailcom> wrote:
> >>>   My problem is that when I try to
> >>> merge the two objects I create, I have tried merge and union I always see a
> >>> middle boundary in between them.  The indicies of refraction are matched and I
> >>> am using fresnel reflection, so I do not see how or why I am seeing this.  If
> >>> anyone has any ideas on how to make this artifact go away that would be very
> >>> helpful.  I have posted the code I used to make the object below.
> >> This looks like a coincident surface problem.  Usually this shows up as
> >> speckles, but in your case it appears to have obliterated both surfaces.
> >>
> >> The quick solution would have been to change the 3.2 to 3.4999 so that the
> >> overlap area is only 0.0001--but that didn't eliminate the problem for me; it
> >> only made it thinner.
> >>
> >> But I like Mike Williams's solution better anyway.  The cast spots seem to be
> >> from the egg-carton topology, although I can't think of why that would be.  But
> >> once you turn on photons, they'll refract into a spotted pattern anyway, so I
> >> wouldn't worry about them.
> >
> >
> >
> >
> What can explain the speckling is multiple total internal reflections. At one
> pixel, you may have only a few, but the next pixel may need a max_trace_level
> near the maximum of 255.
> Have you tried increasing adc_bailout? It limit the number on reflection and
> refractions based on the effective contribution to the colour returned by a ray.
> In some cases, it won't change a thing, in others, it can greatly help, and in
> still other, it may not be acceptable. Only experimentation can tell you if it's
> acceptable in a specific case.
>
> In some cases, adding "all_intersections" can help.
>
> --
> Alain
> -------------------------------------------------
>    My wife is such a bad cook, in my house we pray after the meal.
>     Rodney Dangerfield


So, I tried both adding all_intersections, playing with adc_bailout (seems like
I should make it smaller to decrease the error it permits before "giving up"),
and I played with the max_trace. All of this did not fix it.  Actually, I
looked online and found someone who might have fixed the problem.
http://www.triplespark.net/render/povray/patches/isoacc-patch/
They edit isosurf.cpp.  I am not sure how to do this, I am using MegaPov on an
intel mac.

-Mike

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