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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