In article <3d24b525@news.povray.org>,
 "Florian Pesth" <fpe### [at] compuservede> wrote:

> Ok the media part is copied from the insert menu and worked ok for a simple
> sphere (agate without color_map). I'm wondering what caused the black
> artefact in the middle. Ok it's really not intelligent to place a light
> source in the center of the object, but I don't expected such artefact.

Ok, the black artifact is a common "newbie problem"...for speed, POV 
will only trace through a certain number of levels of passing through 
transparent surfaces or bouncing off reflective surfaces before giving 
up and assuming black. This usually only happens after enough surfaces 
that it is unnoticeable, but in your case you need to adjust this number 
with the max_trace_level in global_settings.

The bright media artifacts...it looks like something to do with the fact 
that you are using a sphere_sweep. The solver for that shape can produce 
inaccurate results, especially with cubic_spline. I would suggest trying 
out your media with a cylinder first...maybe a torus, though that can 
also have problems. Maybe make your own "sphere sweep" with a merge of 
cylinders and spheres, using the spline feature.

BTW, your media settings are...odd. I usually use 1 interval and adjust 
samples, POV will generate more intervals if needed. For this, I'd use 
something like "intervals 1 samples 5", and I usually ignore variance, 
confidence, and ratio (which only has an effect on scattering media 
anyway, as I recall). I don't know why someone would use 20 intervals 
with 1 sample each with method 3...

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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