I've posted the finished image in the povray.binaries.images section, look
for "Cactus Halo".

Thanks for your help.


"Christopher James Huff" <cja### [at] earthlinknet> wrote in message
news:cjameshuff-6DF932.14392730012004@news.povray.org...
> In article <401a832c$1@news.povray.org>,
>  "Felbrigg" <som### [at] microsoftcom> wrote:
>
> > Thank you vary much Christopher, you've solved it!!  I had to set the
> > accuray to 0.000001 to be rid of all the artifacts, but its fixed.
Huzzar!
>
> That's probably pushing the boundaries of what will work, especially if
> you're using functions that are already stretching machine precision
> limits.
>
>
> > I especially appreciate the explanation.  As I understand it, the
accuracy
> > setting is like increasing the "Zoom" on the ray tracings engine.
>
> I'm not sure what you're thinking of, but it just controls the allowable
> error in the isosurface calculations. The isosurface solver just takes a
> series of progressively refined estimates, the accuracy parameter tells
> it when it can stop refining its result and decide it found the
> intersection point. The actual intersection will be somewhere within
> "accuracy" distance of that point. (note that this doesn't necessarily
> mean distance within the scene...scaling can change the relationship
> between what's one unit to the object and what's one unit in the scene)
>
> Anyway, since the value found is not the true value, you can end up with
> a situation where the transparent isosurface is the first one hit, but
> when POV traces a ray from the computed intersection point, it misses
> the green isosurface. Or hits it, decides it's so close to the ray
> origin that it's likely to be an erroneous hit on the transparent
> object, and ignores it.
>
> -- 
> Christopher James Huff <cja### [at] earthlinknet>
> http://home.earthlink.net/~cjameshuff/
> POV-Ray TAG: <chr### [at] tagpovrayorg>
> http://tag.povray.org/

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